Hey man, I was having similar probs with my idle and then came across the os dyno review. Type (os 18 tz 11k tuning) in google and click the 3rd link down. The idle range for these engines ( for the 11K slide carb ) is 6000-7000 rpm. The slide gap of 0.3mm - 0.5mm is very critical. Then set your throttle stop screw so your idle speed is correct. From this point just refer to your manual for the other settings and your car will be flying! It is hard to tune over the internet for many reasons, but the main one is, all settings will vary heaps due to the place you live. Altitude, ATM pressure really play a massive factor for carburetors. Not only for RC cars but all vehicles that have a carbi! Hope I have helped a little.
Kind regards, Shannon