When I ran that set up, everything was 2.5 . The muffler as well. I could only get the GT sound using a Flowmaster 50 Race series SISO offset (not the SUV series).

You can enhance that sound running LT headers w/HF cats welded to the collectors. It sounds exactly like that stang in the transformers movie. My kids even pointed that out

Still running the stock tune.

 

Do you know if that is FlowMaster part#325508 or 425509?
(both are 2.5)

 

50 series race muffler... I honestly have never heard of those before, thats new to me. I've heard of 10 series and 30 series race mufflers.

 

Found it on eBay:
http://shop.ebay.com/items/_W0QQ_nkw...Q_fromZQQ_mdoZ

....but there are two part #s for 2.5"???????

Me want mustang sound too

 

The differences appear to be 325508 is 11.5"s long, and 425509 is 16"s long.

 

The short is a race series ..

The Long is the SUV series..

I have the short race series 50.

 

Perfect. That's exactly what I needed to know.
I have 40 series (I think - it's been about 6 years since I bought it).
I had to get a pipe re-welded at the inner flange into the canister...the welder said it wouldn't last too long so I should look into a new system.

I'm pretty sure I have 2.5 pipes going to it...or 2" maybe.
Anything else I would need Jbrew?