how much better is the gm performance manifold than stock one

 

I'm not real sure about horsepower, but papers show a 7% better flow.

 

better off going with a different one than gm if you're looking for gains. it will be better than stock, but not better than the others that are out right now.

 

Its better but its not the best option. Depends on how much money you got to spend.

 

It only flows about 30 cfm more than the stock manifold while the other headers on the market flow 150-200 cfm more.

 

I have it... and uh, I'm only using mine because it was free for me (my friend ported it out) so mine is free'er flowing that the GMPP unit but it's still restrictive! Save your money buy a true header!

Or if you have a bitchy dealer then you might wanna consider it too...