flowmaster super 44

[Square84]

i just put these flowmaster supper 44's on my suburban. it has a crate 350 and stock manifolds we ran 2.5 inch pipe and a crossover, then the pipes run out the side. this thing sounds like CRAP , on the hwy it has a flapping sound like i'm running on a flat tire. they were supposed to be the same as the 40's only with less interior noise. i'm very dissapointed , and it sounds embarrassing like the freakin stock muffler fell off or has a big hole in it! any body else running thes 44's have the same problem? i'm going to have to start from scratch. soory for rambling but i needed to vent after taking a $300 dollar step backwards today. -Nick-