yea dude, when u get that 2.5, you dont adjust it when u first get it. You run it on the stock settings traxxas gives you, then after your 3rd-4th tank you can slowly adjust the high speed needle. Usually you would give it more lean because the traxxas settings are rich....or should be.

I have the Traxxas 2.5r in my nitro 4-tec and it runs great. Also make sure you break in the engine the way traxxas tells you or you will have problems.