I put stainless y pipe behind exh manifolds eliminating the pre cats which are not required,passes emmisions, random cat and another stainless y pipe and duel chambered mufflers on each side,polished tips all from Mid America and the cost was low.these pipes and mufflers sound great

Make sure your tips stick out beyond your bumper. I just made that adjustment on mine and it made world of difference.

I have Corvette Centrals "H" pipe true duels (cat-delete) coming out to Mid America Motorworks Quad Power Mufflers on a stock '89 L98.  Very free flowing.  Is loud but sounds great.  

Mt 91 had a full Magnaflow on it when I bought it, including hi flow cats. Great sound but loud, you cannot have a conversation in the car. Switched the straight through bullet like mufflers to Flowmaster 50s'. Lesser tone but just as loud and just as much drone. That was $250 wasted. I may end up going back to stock mufflers, with the hi-flow cats, it'll probably still be a little louder than stock but easier to live with than what I have now.

My '87 has simply got a dual 60mm s/s pipe system all the way from the stock headers out to two small boxes at the ends which are sleeved to negate their effect, no cats or other restrictive items. Its sounds great and idles nicely. Driving, its quiet enough that I can hardly hear it even with the roof off, but with a free flow filter etc, it'll waken the dead with an awesome V8 soundtrack when I tach it up.. No drone either at any speed. In fact, at a car show, I won the best exhaust note beating a new MB 6.3 V12 gullwing complete with its stock cutouts!!