is there much of a difference between the supper 44 and the super 40. The reason im asking is because i would like to get a high flow cat and go with a bigger pipe. So i would either stay with stock pipe dia. and my 44 or ill go bigger with a 40. Is it worth it to go with a little bit bigger pipe.

 

It is all in the design. The Super 44 is supposed sound deeper than the Super 40 as well as have better resonance control. It all depends on what it is installed on and what the system looks like.

FlowmasterMufflers.com has some descriptions and Youtube has some comparisons (albeit some with pretty crappy sound quality). HERE is one although I think it has the original 40 series, not the Super 40.

I am trying to figure out what model Flowmaster mufflers I have on my K5. I just cut the system off in preperation for the new 2-1/4" Hooker dual exhaust kit (pn 16528HKR) and the new Hooker headers (pn 2453HKR). I think they are the original 40 series. They were on there long enough for the tail pipes to rot off, but the mufflers are still in very good condition and I was able to get the old pipes off of them easily.

 

This won't directly answer your question, but it is an interesting video with one of the honchos from Flowmaster.
Flowmaster Video