How much difference will a LS2 intake give me compared to my LS6?

 

You will lose power with the LS2 intake manifold. The LS6 out flows the LS2 intake very easily.

 

A ported LS2 intake with a 90mm tb will easily outflow an LS6 intake. It will even outflow a FAST out of the box (but not a ported FAST) if done right. Unfortunately you get alot of advice from people who don't know what they're talking about and regurgitate what they've heard from someone else who didn't know what they're talking about.

So if you can get it ported and match a 90mm TB to it, expect a 15-20hp gain over a stock LS6.

 

the ls2 will flow better but might not bet worth the cost for the little bit of incress, but you can step up to a 90mm tb, relocating the map is requiered.