30% percent shouldn't make it harder to tune, but traxxas fuel is too oily. i would switch to sidewinder or o'donnells. traxxas has too much oil(18%), where as most have 12%. but if you wish to drop down to 20% nitro, set the highspeed to 3 3/4-4 from closed. if you stay at 30% set the high speed to about 4 1/2