if its burning(dull grey filament) then it means u have less fuel for burning.
but mostly its the head shim clearance that caused this sort of problem.
unscrew your heat sink and button head from the sleeve. add 1 or 2 more 0.1mm head shims between the sleeve and button head. still in doubt, just richen your high speed needle it should be ok if its not too hot.
just my 2 cents