I have a 2007 Silverado ,ext cab, 6.6 bed ,4x4 ,5.3v8. I am thinking about putting on a Gibson headers,and cat back sinlge side exhaust. Just woundring if it is worth the money?

 

The headers wont help.... stock ones are pretty much the same.
If you want any performance from headers youll need to go with long tubes.
But this will move your torque in the RPMs... not really that great for 4 wheel'n when you need the torque at a lower rpm.

Cat-back will help some... but really all you need is just another muffler. The exhaust piping is actually pretty good. I cant speak for the 6.6L, but I am sure its 2 3/4 with manderal bends. The same pipes you will get with the cat-back system.

Just get yourself a muffler and a tip.

I cut mine off and used a hooker aerochamber with dual 2 1/2" outlet dumped. Its really not all that loud, but does have a little bit (and i stress little!) drone in the cab at 70mph on the highway.

 

Is there any major difference in engine response if you would change exhaust manifolds to headers? I have an 07 silverado 5.3L.