I am running the Pixy Black Chrome head that has been modded by Murnan. This thing is unbeleivable. It is not even broken in yet and I have not really gotten it hotter than about 220 degrees and it just out right flys. It has great bottom end as well as top end. I also had a non modded version and I was very impressed. I am also running 30% nitro and have not had any toruble out of either of my engines.