from experience, what is the most added h.p. you guys have seen a new (custom) exhaust system provide over a stock exhaust? not necessarily Camaro related, just in general.

Hey Mark,

Long time no see.... I would guess to say 25hp sounds about right.

Depending on how restrictive the "stock" system is Vs. the "free flowing" aftermarket ....

1hp - 50hp ???? I guess and that depends on the motor mods too :)

Its rather an open ended question as indicated by posts above
What is the current exhaust sytem like?
Size of engine?
What is the intended use of the vehicle?
What rpms?
Going from headers to cast exhaust will increase HP and torque down low...