i have flowmasters on my z28 and i was wondering if maybe there is another brand that could possibly give me more power and still sound aggressive

if your urnning your exhaust all the way to the back of hte car, then you dont have to have a quiet muffler. i would recommend dynomax ultra-flows, moroso spiral flows, or flowmaster super 40's. im not really a big fan of flowmaster, but a 40 series is louder then the one you have. the dynomax and moroso spiral flows pretty much have no restiction at all, but will shut up your engine a little bit.