I got a 99 gmc suburban 2500 with a 6.5L in it and i really want to change the stock exhaust. i dont really know whats out there for this engine especially since majority of what i found out there was for the duramax. Ive had a bunch of people tell me to go 5" but i dont even know if anyone makes a 5" for this engine unless its done at a exhaust shop. I would also like to get that nice whistle the turbo makes which im assuming put a downpipe to straight pipe back? oh and is the cat needed? i have an L65 engine code if that would help at all with anything.

Give Heath Diesel perfromance a call they are the 6.5 specialists and will get you the best possible exhuast to suit your needs. I almost forgot to add Kennedy Diesel he to has good experience with the 6.5. Check out either one at kennedydiesel.com or I think the site is heathdieselperformance.com or heathdiesel.com

I had a 92 6.5 and no cat. I ran 3.5 inch banks and it worked fine. Personally for that application, I think it is overkill to go 5". If I had to do mine again, I'd go 4" and call it good (in your case, cat delete of course). I don't think you'll hear much whistle. On mine, stock boost was 5psi and with the banks kit I had, the boost was increased to 10 psi. Not sure what your vintage of 6.5 was set to.

On edit: yeah what Avery said.

thanks man i appreciate it

yea the 5" doesnt really matter to me, i think 4" will be fine too i just want something thats loud. im an exhaust nut and love a good sounding loud exhaust. i noticed bully dog makes an exhaust for the 6.5 but i dont really know how its gonna sound. im very picky with exhaust. I went thru 4 exhaust options on my 07 mustang gt before i got the sound i liked. i like to do my research and make sure im getting what i want but i have to go by what other people recommend so i just have to trust the word of others

it might have been banks that had the exhaust system for it and not bully dog its one of them

Heck even with that 3.5 inch exhaust, that 6.5L of mine sounded like it actually had muscle heh.