Downpipe Exhaust/Test Pipes for 2003-2006 Nissan 350z Infiniti G35 With Gaskets And Bolts

Fitment

2003-2006 NISSAN 350Z (Z33 Chassis) VQ35DE

2003-2007 INFINITI G35 (V35 Chassis) VQ35DE

If you like this 1999-2006 4.8L, 5.3L, 6.0L Test Pipe, please feel free to buy it; after purchasing, you can always contact us for a full refund if you don't want it.

Q1: What exactly are test pipes, and why do people swap them on 350Z and G35 cars?

A1: Test pipes are basically straight sections of pipe that take the place of your factory catalytic converters. The stock cats on a VQ35DE are bottlenecks — they're designed for emissions, not flow. Slapping on test pipes opens that up immediately. The turbo spools faster, you pick up throttle response, and the exhaust note gets noticeably meaner. Most guys running NA builds on these motors add them early because the VQ platform responds to exhaust mods really well.

Q2: Will test pipes throw a check engine light on my G35 or 350Z?

A2: Almost certainly. The downstream O2 sensor sits after where the cats used to be, and when it sees no catalytic activity, it flags the CEL. That's just how the system works — it's not hurting your motor. You can clear it with a tune that disables the rear O2 sensor functionality. Leave it tuned to stock and the light stays on. Some people just deal with it, but honestly it gets old staring at that dash light every morning.

Q3: Do I actually need a tune after putting downpipes on my VQ35DE?

A3: Yes — and I'd say skip the tune at your own risk. Without recalibrating the MAF and fuel trims, you'll run rich, which means carbon buildup on your plugs and potentially fouled electrodes. You're leaving real power on the table too. A proper downpipe tune adjusts the closed-loop fuel mapping, fixes your rear O2 sensor readings, and gets the AFR where it should be. ECUtek, HKS F-CON, and similar platforms all support the VQ35DE. The difference before and after is night and day.

Q4: Catless or catted — which downpipe should I go with for my 350Z?

A4: Depends on how you drive. Catless (test pipes) gives you maximum flow and the loudest, most aggressive sound. If you're building a track car or a weekend warrior that never sees emissions testing, this is the move. Catted downpipes keep a high-flow catalytic converter in the mix — you'll sacrifice a little top-end power but keep the O2 sensors happy and the CEL away. One thing worth mentioning: if you're in California, catless downpipes are flat-out illegal for street use under California Vehicle Code Section 27156. No exceptions, no loopholes. You'd be limited to off-road and track-only use there.

Q5: What kind of power gains are we talking about with downpipes on a G35 or 350Z?

A5: On a bone-stock VQ35DE, test pipes typically add 8 to 15 wheel horsepower depending on whether you go catless or catted. Dyno pulls on these motors consistently show 10+ whp gains when the car is tuned properly. Stack that with a cold air intake, shorty headers, and a cat-back, and you're realistically looking at 30 to 50 whp from bolt-ons alone. The VQ responds well because it was strangled from the factory — the stock exhaust is genuinely restrictive.

Q6: Will Flashark downpipes fit my 350Z and also my buddy's G35?

A6: Same motor, same downpipe. Flashark test pipes for the 2003-2007 350Z and Infiniti G35 are engineered as direct bolt-ons for the VQ35DE platform. Whether it's a Z33 coupe or a V35 sedan, the flanges, donut gaskets, and mounting points line up with factory specs. No welding, no fabrication, no grinding down flanges to make them fit. One kit covers both chassis — that's the nice thing about these cars sharing the same engine from the factory.

Q7: What's the difference between test pipes and a full downpipe assembly?

A7: Test pipes are just the straight sections that replace the cats — they bridge the turbo outlet to the y-pipe. A full downpipe assembly includes everything from the turbo elbow all the way back, often with an integrated flex joint and sometimes a high-flow cat built in. For most street builds, test pipes get the job done at a lower price point. If you're pushing serious boost with a turbo or supercharger kit, a full downpipe with a flex joint handles the movement and heat expansion better without developing leaks.

Q8: Can I install downpipes on my 350Z/G35 in my garage, or should I budget for a shop?

A8: It's absolutely doable in your driveway if you've got basic hand tools and jack stands. Figure 2 to 4 hours if you're not rushing. The job involves lifting the car, pulling the undertray, unbolting the factory downpipes from both the turbo and the y-pipe, then sliding the new ones in. You'll want penetrating oil for the turbo studs — these get seized on high-mileage VQ35DEs, and nobody wants to snap a stud when they're this deep in the car. While you're in there, throw in new gaskets and hardware. Everything comes in the Flashark kit.

Q9: Will downpipes fail my emissions test?

A9: With catless test pipes, yes — almost guaranteed. During a standard OBD-II inspection, the technician's computer checks catalyst efficiency through the rear O2 sensors. No cats means that monitor never completes, and you fail immediately. In states with strict emissions enforcement like California, Colorado, or New York, this is a hard fail. California's Vehicle Code Section 27156 explicitly prohibits removing or bypassing the catalytic converter. The workaround is running catted downpipes for street legality, or keeping your stock downpipes on hand for inspection day and swapping them back for track use.

Q10: What material should downpipes be made from, and does it actually matter?

A10: 304 stainless steel is the baseline you should accept. It holds up to heat cycles without cracking, won't rust through after one winter, and looks decent under the car long-term. T-304L has slightly less carbon, which makes welding easier and reduces warping around the turbo flange. Mild steel downpipes are cheap but they'll be surface-rusted within months if you drive in the rain or anywhere with road salt. The cheap stuff ends up costing you more because you'll replace it. Budget brands like Berk and Stillen use 304L, and Flashark matches that spec at a friendlier price point.

Q11: How much does the exhaust sound change with downpipes?

A11: Big time. The stock VQ35DE exhaust is tame — almost muted. Test pipes open up the bark considerably. You'll hear more turbine and wastegate chatter, a deeper mid-range tone, and that V6 spool character behind the seat. It doesn't get raspy or obnoxious like some four-cylinder builds — the VQ stays refined but sounds properly aggressive. Highway drone can show up depending on your mid-pipe and muffler combo. Quality downpipes with flex joints cut down on vibration transfer into the cabin compared to rigidly mounted budget pieces.

Q12: How does Flashark stack up against brands like Berk, Megan Racing, or Stillen?

A12: Flashark uses the same T-304 stainless construction as the established names — no compromises on materials. The difference is in the details: CNC-machined flanges that drop in without hammering, mandrel-bent tubing for unrestricted flow, and every gasket and hardware piece included in the kit. Some budget options arrive with warped flanges or misaligned bungs that require you to weld or modify them to fit. Flashark comes out of the box fitting like factory parts. For the guy who wants proven materials and solid fitment without paying the "premium brand" tax, Flashark hits the mark.