Originally Posted by
MassiveMods
The stock .21 shimming from factory is .55 1 x .3.5 and 2 x .1 with standard head button , if you were to go to 30% nitro id pop in the extra shim to bring it up to .65 or stay at .55 and convert to turbo head button .
So what your saying is at 20% I should leave the shims.. thought it was shimmed for 30?