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ZZP GXP Downpipe

Stock downpipes are double-walled tubing with an inside diameter of just over two inches. Gains of over 10HP have been seen along with a substantial drop in knock. This part can typically be installed in under an hour.

Our downpipes are made from high quality stainless steel. Even the flanges are stainless, which isn't something any other company offers. This ensures a lifetime of rust-free operation and eliminates the need for paint that could flake off. Stainless costs a little more but we feel it's worth it. All welds are held to the strictest of quality control standards to ensure a professional finish. Our weld quality is higher than any other downpipe manufacturer. When shopping around, ask if the downpipe is 100% stainless, and ask for a close up shot of their welds. Compare them to ZZP's downpipes, and it will be apparent why ZZP's downpipes are leaps and bounds ahead of the competition.

Exit option: The default, or stock, downpipe exit will come with a 2.5" flange. This is the stock size and will allow you to bolt it in with the stock exhaust, or any aftermarket 2.5" catback. If you have a 3" catback, or are planning on purchasing a 3" catback, you will want the 3" exit option. The 3" option will not fit with the stock exhaust. 

Bolt in with cat downpipes can be used on stock to highly modified cars. We use Magnaflow, high flowing catalytic converters. They bolt into a stock or aftermarket cat back exhaust system. They include an O2 bung for the rear factory O2 sensor. 

Interlock flex (sometimes called turbo flex) is the best flex money can buy. Typically, the downpipes in our market use a single wall flex. This is durable but has a ribbed inside design that can disrupt airflow. This type of single wall flex is what people are running when you hear them complain about a whistling or ticking noise coming from their exhaust section. To remedy these issues, you can buy a double braided flex which has braided stainless on the inside, as well as outside, of the flex. The problem is that they fail very easy on supercharged cars. Interlock flex is the 3rd solution and while is costs more, it is the best. It withstands the higher temperatures of boosted applications and provides a flat smooth surface for the exhaust gas to run over. 

Please use factory torque specs when installing our downpipes.

Fits 5.3L Impala SS, Monte Carlo SS, and Grand Prix GXP. Does not fit Bonneville GXP. 

Shipping charges are based on dimensional weight.

Our downpipes come with a high flow catalytic converter that is 48 state legal. Our catalytic converters will not pass California or New York state emissions. Please contact if you have any questions.

We are currently offering $100 in store credit to purchase your stock catalytic converter back from you. If you're interested, take a photo of your stock downpipe and email it to We will provide prepaid shipping labels for domestic (U.S.) shipments.

Customer Reviews
4.8 Based on 33 Reviews
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Maxime P.
Canada Canada
Monte carlo ss 2006 ls4

Very good spark , got instant power

Woody D.
United States United States
Quality made

The pipe is pretty, though my P0420 code came back after a week the part still functions well. It took forever to get because of circumstances unforseen, it was worth it.

Stephen O.
United States United States
Gxp downpipe

Works and sounds great. Very satisfied

Bryce S.
United States United States
gxp grand prix downpipe

adds a good tone

Ryan R.
United States United States
07 GP GXP + GXP Downpipe

Bought this downpipe to replace the stock unit and it sounds really good and you can definitely tell it’s flowing better with my CAI. Installation was very easy and everything lined up perfectly. Only issue I had was rust but that isn’t the parts fault. Just keep in mind you’ll need to get yourself header to dp and dp to resonator gaskets, as they are not included. Overall, still a great purchase and won’t be my last.