just asking ive been planing to change my dads hummer 3 exhaust but since im not from the U.S aftermarket/OEM parts for our H3 is by"personal import only" so my plan is just have a local butvery reputable ( this shop makes exhaust for lancer evolution, mustangs etc,,,)exhaust shop so my question is whats the ideal diameter for my dads H3 exhaust and intake. ive already installed a K&N drop in filterbut ifeeli can extract more hp and have a better mpgfueleconomy inour car.

 

Exhaust by itself will not get you much, 2HP MAYBE? It will get you some nice tone. 2.5 inch is all you need with a 5 banger.

Check this out http://www.magnaflow.com/02product/s...ll&id=6172

 

sir whats the stock exhaust diameter ? just for comparison?

 

Stock exhaust is 2.5". I removed the stock muffler and welded up a dual exhaust tail pipe with stainless tips. My cost was about $50 US. But I did my own fab work. Sounds nice, not loud. I'll see ifI can get a pic or a link to what I built.