i have a bone stock 89 Formula 350 Firebird and would really like to upgrade the car's exhaust. My question is if i upgrade the exhaust to an aftermarket setup, like flowmaster or magnaflow, and my car is completely stock, would i notice any loss in HP or torque? i know its possible to make gains in these values but i've heard from a few people that upgraded the exhaust might acutally do the opposite.

what do you think it will do? and what information is this based on? thanks!

 

You will definately gain, the stock exhaust on our cars is very restrictive. You don't want to go huge, or the pressure drop from the Y pipe to the I pipe will kill the exhaust velocity. Just do a 3" catback, and then do a set of shorties, high flow cat, and a good Y pipe and you will be set.