ceej, what is the spring rate of the new springs and do you know the spring rate of the old mightyboy ones??? i would assume they would be the same as the hatch spring rates 1.48kg/mm, but not 100% sure. also have you looked into the hatch 800cc NON 3-leaf rear setup 2.17kg/mm as opposed to the std ...

new to Mightboys's come from motorbike background so not sure on specifics, but it could also mean incorrect jetting as a better flowing exhaust system will cause a lean mixture at mid-high rpm (low rpm isn't really effected unless you do some porting to the head). also look for small exhaust leaks ...