naw even n/a cars need some kind of good flow of exhaust gas to run its best. (i,e max hp, tq) just to much of a flow of exhaust on a n/a car loses torque and kills the cars perfomance more than it helps. for example....

when i worked at my last shop with the dyno, i put a buddy club spec 2 exhaust on my eg hatch. (its a straight pipe, with one small resonator). true 2.5 inch exhaust.
it picked up hp over the exhaust i had on the car before. but lost tq. i put in the silencer just for shits and giggles and i made more tq than i did before, but lost 2 or 3 hp. but all the 3 inch exhaust i have seen on stock motors dont do shit, but cause the car to lose torque and make alot of noise. but all the n/a guys i have followed in n/a drag racing at least use the big collectors/exhausts but finely tuned headers to make up for the loses the normal motor would lose with a huge exhaust.