I recently just rebuilt my 350 in my 71 cutlass conv.
The exhaust sounds great till about 2000 rpm then its real loud and raspy sounding.
I have hooker headers
-flowmaster 2 1/2 pipes with an H pipe
-I put magnaflow mufflers on it.
It sounds good till 2000 to 2500 rpm then after that it sounds good again.
What would be the easist way to quiet this down?

 

You could try a 12" resonator at near the end of the tail pipe. This has worked well for me in the past. In fact I will be installing a couple on my 57 Olds. The 455 with the 2.5" pipes is two loud under acceleration

 

The resignators might just do the trick.
I found it hard to beat the sound levels of DynoMax super turbos. They work good and it's all I use. I don't like to draw too much attention to my car when I'm getting on the gas.