So i'm about to start breaking in my new 28, the instruction say that for 20% nitro I should run 3mm shims, my engine came with a silver one and cooper shim already installed, the cooper one is thinner than the silver one. is that 3mm or more? less? should i just leave it alone?
can someone please hell me here please.

also I wanted to say thanks to racernine for the help. those guys are pretty good at helping people out.
I got that SH pipe.

thanks