G'day Mate,
OK first things first, running a motor rich, does not mean adding more lubricant, to the fuel,
I run all my engines on 18 to 20% coolpower oil, no castor, 2 strokes use #8 OS plug.
Your 46 FX should be running an 11x 6 or7 prop.
When you changed the piston & liner, did you run the motor in again? Because that is like having a brand new motor, after all, these are the things that need to be bedded in when a motor is new.
What size prop are you running, what amount amount of oil, you said 15% Coolpower & 15% Omega, is that oil content or nitro content?
If it is 15% oil, you need more, 18 to 20%.
From reading your post, you said, it would not run past half throttle, that means it is too lean on the main needle valve.
Ok how to check & see if you have a problem,
Start the motor, run it up to full throttle, if it won't run past half way, open the main H/S needle, 1/2 turn anti clockwise, keep turning it out until it WILL run to full throttle, then, hold the plane nose high, & listen to the engine, it should pick up revs as the nose is raised, if it does not, it is too lean, richen some more & try again until it does speed up slightly, with the nose raised, if you can't get it rich enough, then there is a blockage in your needle valve or fuel system, clean it out & try again.