put the restricter that come with iit in for fuel conservation. and never..never never never touch the mid. i have one in my savage basher and my friends got one he tuned the mid a hair and now he has a new engine that he cant even use. i run 30% in everything i have so i do alot of tuning during break in on all my rc's. i tune the top and the low and it was perfect. and it keeps a good tune. the only engine that was ready for 30 out of the box was the .21 Go 7port i have. axial makes good affordable motors. 125cc gas tank. restrictor in place. 8 minute run time.