RE: .60 engine recommendation?
I have not had the rich mid range problem. Funny thing is I use the low cost, budget glow plugs from Hobby People. If after tweaking the needles and it does not go away, try am Enya #3 plug. That is my favorite plug of all time. They are not cheap. For me, I think they work way better then the O.S. plugs.
Buzz.