RE: Evo 61 engine issues...
I don't have any explination other than the engine is a great runner.
Have another set of eyes check your fuel lines. My .61NT ran
2250 idle and 11k+ top-end without so much as a needle tweak.
I run a 12x6 APC, Wildcat 15% in a Vector Flight 60" Sukhoi.
Flys it super.
Have you changed the factory needle settings?