I had a lot of trouble in the beginning with the 61CXLR with pipe because I was using the wrong pipe length. After I got the pipe set at 20" then it was awesome, super speed control with lots of power.
The setup, as you know, will depend on your model, weight, drag, line length, prop etc..
You are right on about the fuel. I found the exact same thing.
Suggest you try using the pipe from 19.5 to 20.5
I use Enya 4 plug and when it gets in the 90s the Enya 5
Also try bigger venturis, Enya has 8.0 8.5 and even 9.00 . I like higher fuel consumption, better lub and lower temperatures.
Play with head gaskets to set the engine in 2-2-2, 4-2-4 or get the high compression head to get a 4-4-4
My Thundergazer with this engine is awesome. Many times I flew in heavy windy conditions and I did not suffer as much as the other guys. Last Brazilian NATS I participated I finish 3rd in Open with it. Not bad for some one that learned the pattern 4 years earlier
The Speed regulation and the Power of this Enya engine definitely help me a lot and gave me the power advantage. Treat this engine as if it was a 75 and all will work fine.
I setup mine to run in 2-2-2, pipe at 20" 8.7mm venturi 13x3.75 B.E 3B prop 10 to 15% nitro depending climate. My T.G is at 70oz and there is no problemo flying at this weight with this engine and 69' eye to eye lines. Laps 5.7s Iit does not get much better then this.
Martin