i have been working on my son's 90 auto. it sounded terrible with gutted cats. the next step was to gut the resonator. now you can here the super charger though the exhaust. my son says the most seat of the pants gain was made with the resonator work. he still has the factory mufflers. the outlet side of the resonator was cut off, then the inside was gutted. the small tubing was then cut from the ball and a peice of three inch tube welded on, it fit very nicely. next the other side of the ball is opend up to two and seven eigths. midrange seems to have been helped out.