How much horsepower will an exhaust add


Asked by Jul 20, 2012 at 03:39 AM about the 2000 Pontiac Grand Prix GT

Question type: Car Customization

I have a 2000 grand prix with the 3.8 in it, ive added a magnaflow cat and then dual SLP flowthrough mufflers, plus high output coil spark plugs and msd wires. About how much hp do you think ive added from the original 205hp

Also i have a 91 k1500 silverado that has an aftermarket throttle body, cold air intake, perfomance headers and cat, and glass pack muffler, also msd wired and high output coil. stock was 210hp.

3 Answers


By opening up the exhaust you can free up some HP, maybe 5-10HP max. Throttle response is probably better as you noticed, but negligable in the power department. Only real way to know is put your car on a Dyno. The quoted HP of a car is with the engine run on a stand, so the HP has to go through a drivetrain, so you lose some there. 20% less HP than stated on avg. with an automatic. Less for a manual.


no tuning done on either? both probably gained anywhere from 5-10 hp.

yup i would say around 5 hp.

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