OK lets see if Ive got this understood correctly.

My engine, an OS46 FX, has had about 4 litres of fuel through it now, 1 litre on the ground running smokey rich the rest in flight. Ive set the high end needle valve so that when I reach a peak in RPM, I richen (wind out) it 3-4 clicks. After some difficulties with it spluttering and dieing (always after landing thankfully) after a long idle period, like on an approach, a mate (Vortec) suggested I lean out the idle valve, about 1/8th of a turn, after starting it and running fast for a few seconds I let it idle for about 10-15 secs and it races to life, no spluttering or dieing etc. Which we had to do twice to get it right. BUT if I let it idle for longer, like a minute, opening the throttle quickly produces smoke, noticeable oil/fluid from the exhaust and it splutters away for a few secs before reaching peak RPM. This worries the heck out of me as Ive been practicing my landings doing touch-n-go's. It hasnt yet actually stopped on me though. Today while flying it I noticed an almost complete lack of exhaust smoke and the oil on the tailplane after flight wasnt its usuall greenish colouring, more grey. I immediately thought its too lean. I richened it 2 clicks and after the next flight it was more the usuall greenish colour. BUT after idleing for an approach, the spluttering on applying full power was even worse. In testing on the ground, it takes maybe 10-15 secs to reach its lowest idle RPM after running flat out, then the idleing gets sort of rough, like its missing a bit.
Do I now need to lean out the low end just a fraction so it will idle for a longer period and reliably achieve full power again ? Am I right in assuming the oil on the plane after flight shouldnt be a greyish colouring ?
I hope the above makse sense.