All of my OS engines cackle a little bit at certain speeds but never at full speed!

My plug I am using is an OS #8 and I just put that in new last week. It has a good glow to it right now also.

Actually after flying it 8 times earlier this morning I was getting so tired and lonely there from no one else there flying, I decided to pack up and worry about it later. It didn't do it as much when I first had my 14-8 apc prop on it today but when I put my 13-8 apc back on it got worse.