S366 lag? Sounds like big tire syndrome to me:roflmao:
If I were to do it again, and they weren't available when I purchased my current manifolds and up pipes, I'd spend my money on the HSP set up.
Reason why is the unitized single plate connected port construction vs having individual rnunners like say, PPE manifolds....
My manifolds aren't true, or square or flat anymore, however ya want to put it. They rock back n forth if you place them on the ground and a straight edge reveals they're no longer even, they warped a bit
I'm gonna either have to deal with it and constantly check the bolts and make sure they're tight, or have the manifolds milled or decked, whatever it is that will make them "even" again
Having a single plate clamping against the head and keeping the runners all connected like how HSP builds them would keep anything from twisting and warping from heat cycling
To echo everyone else, Gears will help the most in your case. I'm only running 35's and I upped my gears to 4.11 and couldn't be happier:thumb: they helped in every way.