As for tuning idle mixture i read great trick on how to do this. Make ur engine run at idle then pinch fuel cable (engine will stall), but before it stalls it should rise rpm a bit. If it doesnt rise at all - u run too lean. If it raises hundreds of rpm - u run too rich. It took me 5 minutes (it is almost week that i have my first nitro) and my engine now works great. Then u adjust idle speed (gap on throttle). Set idle speed so that clutch doesnt engage. As for high rpm needle u have to try your car at high speed. Mine was too lean and at half open throttle it didnt want to gain rpm. Unscrewed it half a turn at a time and now it rockets from 0 to max without hesitation. IMPORTANT NOTICE, for tornados xp/xl and alike use hot glow plug (helps to tune idle speed). At first i used OS R5 (almost coldest one) and 5 geeks coulnt tune it, changed to OS A3 (one of the hottest) and tuned properly in 10 minutes