I recently purchased Kooks 1 7/8 headers and catted y pipe for my 2010 6.2 Sierra. I was disappointed to find that the y pipe is only 3" after the merge which is actually smaller than the 3 1/2 factory catback. I am told this is best for this application. Kind of hard for me to beleave considering the Kooks 6.2 l99 Camaro exhaust goes from duel 2.5" stock to duel 3". I think rather they adapted what they already had to fit this application. Same can be said for the Corsa cat back. It is actually only 3" with a 3.5" socket to fit at the front of the catback. If I had it to do over again I would definitely go with the ARH setup. I spoke with ARH directly. They told me their system is a full 3.5" after the merge on the y pipe. Moving on, yesterday I decided to go ahead and install the Kooks system. The headers have a great fit in the engine compartment but I have another issue with the ypipe. It seems like its too long. It actually goes about 6" past the expansion joint on the factory exhaust. Has anyone else ran into this problem? I think its going to be a loud trip to the exhaust shop.

 

I'm having issues with Kook's too at the moment with my Y Pipe, but I have a 2008. Try calling their tech support line.

 

My Dynatech's are also 3 in at the merge. The power gain would be negligible, unless you were running big power, right?

 

My feeling would be that gm wouldn't throw 3.5" pipe at a truck for no reason..

I have kooks on my trans am and would never get another set huge fitment issues and the y-pipe is a PIA to get on/off, ARH for me next time also.

 

Maybe the 3.5 makes up for having 3 cats...

 

What do you mean? Theres only two cats. One behind each manifold, then ypipe, then flex/expansion joint, then resonator, and last a muffler. There is no third cat-on a 6.2. At least not on my 2010.

 

This is why I'm glad I got the 2007-2008 headers and stock cat-back to put on my truck. Full 3.5" all the way out.

 

On the 5.3's, that "resonator" you speak of is a catalytic converter, can't remember if the 6.2's have the same setup. The real resonator on the 6.2's is over the axle. A resonator works best at the end of the exhaust system.

 

You are correct muffler then resonator over the axle. I had it backwards.

 

So wait, was I right? I have never seen a 6.2 exhaust as mine came the way it is. I have def been known to be wrong. Just figured my 2010 5.3 had a similar setup...