What jetting do you suggest for my stock 400ex when I add a Stainless Yoshimura complete system? It currently has a stock headpipe with an FMF Powercore IV slip on and the jetting is a little lean now. Warning! The Powercore IV is a complete POS. I was a fan of FMF, but this item bites! It is the replacement for the original that fell apart and this one faired no better no matter how much I tried to maintain it.Sorry, but the thing is now seized on the headpipe and heat and an air chisel can't release it so I'm getting the Yosh.
Please advise on the jetting, I ride in the Glamis/Gordons/Buttercup area so mostly @ sea level.

 

if your only mod is the yosh pipe, put in a 155 keihin mainjet. i would also pop in a 42 pilot jet.