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ZZP 3800 Downpipe

Exhaust - ZZP 3800 Downpipe
Exhaust - ZZP 3800 Downpipe

The stock downpipe uses double-walled tubing with an inside diameter of just over two inches. Following the restrictive downpipe section, the stock unit subjects the exhaust gases to the choking effects of the catalytic converter. After the cat, it flattens out into a section dubbed the infamous "U-Bend," which is a section of pipe crushed into a "U" shape by GM in order to fit a rear o2 sensor. This section has less volume than the same length of 2" pipe, and approaches the volume of a 1.75" pipe with the rear o2 sensor in place! Our downpipe eliminates all of the aforementioned problems! Gains of over 15HP have been seen, along with a substantial drop in knock. Most users can drop a pulley size and/or eliminate 5-7 degrees of knock. This part can typically be installed in under an hour.

All downpipes are sold with a high flow catalytic converter. 

Our downpipes are made from high quality stainless steel. Even the flanges are stainless, which isn't something any other company offers. 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, ask if they use stainless and for a close up shot of their welds. Compare them to ZZP's, and it will be apparent why ZZP's downpipes are leaps and bounds ahead of the competition. They are guaranteed leak free and feature high quality welds, laser cut flanges and 16 gauge metal. We have test-fitted our bolt-in pipes on both stock and modified cars with perfect fitment. Our pipes even include the slight factory angle offset on the flange.

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 possible option. It withstands the higher temperatures of boosted applications and provides a flat smooth surface for the exhaust gas to run over. 

Most common downpipe gaskets can be found here, exhaust manifold to downpipe inlet gasket, downpipe to factory catback/2.5" catback gasket.

04+ Grand Prix' (Series III cars) will require a style "B" o2 extension for the rear o2 sensor. 

Please use factory torque specs when installing our downpipes.

This downpipe is not compatible with any aftermarket headers, it is designed to fit the stock OEM rear manifold.

*Shipping charges are based on dimensional weight


This will only fit the 3800 v6 engine, does not fit LS4 V8 cars, if you have an LS4 powered car, you would want our "GXP" downpipe instead.

This fits on all the following cars:

  • 1997-08 Pontiac Grand Prix with 3800 Series II engine-Both Supercharged and Non-Supercharged cars
  • 2000-05 Monte Carlo 3800 3.8L Engine Only
  • 2000-05 Impala 3800 3.8L Engine Only
  • 1997-04 Regal 3800 3.8L Engine Only
  • 1998-99 Intrigue 3800 3.8L Engine Only

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.

Exhaust - ZZP 3800 Downpipe
Exhaust - ZZP 3800 Downpipe
Customer Reviews
4.8 Based on 280 Reviews
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Filter Reviews:
United States United States
Great product

This downpipe is a great product and constructed with the best materials and the welds looked good. Definitely a huge improvement over stock. I retained the stock manifolds so the only issue I had was I had to make some adjustments to the bolt holes to get it to bolt up to the stock manifolds but outside of that all was good and I'm happy with the upgrade.

Jeffrey H.
United States United States
Always good

Fits perfectly always had good history with their parts

United States United States
Excellent product

Recently installed this downpipe on my '02 GTP and it was very straight forward and it fits and functions as designed. Only problems were removing the stock hardware and I would recommend you get an exhaust ****** stud and nut kit (Doorman part number MM03142) just in case you break one off. I got mine out but the studs backed out of the manifold so I replaced them the Doorman kit. All in all it is a great, well made and good looking part, shame it is under the car and can't be seen! The car has a little more bottom end and is not much louder than the stock unit.

Kirk M.
United States United States
Impala '04 Tucson, AZ D.O.T. POLICE spec Restomod.

I have NO experience using them. They are not installed because I don't have any gaskets or fasteners included. When I write customer service regarding parts or loudness or drone or solutions. If I peck out painstakingly five questions, only one will be addressed. That is discouraging. And again "Out of stock" is disappointing. I have received numerous parts That thier appearances are off the charts fabulous!!! 3800 ZZZP W-body Coilovers, ZZP frt / rr Sway bars, CPU upgrade #1.0, Frt control arms and bushings, Fuel filter, Frt PLOG, Rear PLOG, CERAMIC Heat resistant treated CROSS OVER PIPE, 12" GTP rear rotor/caliper kit. 10.5 mm plug wires, NGK Spark plugs. New short Dog Bones, W/ polyurethane bushings, And many others that I wish were available. All ZZP Parts. Terrific stuff!

John L.
United States United States
Very nice

I bought one second hand for a STEAL!! Sitting around for 3 years,and it looked new?? Very nice part!! Saw a difference in response and top end improvement!! ZZP rocks