well, i had been having this problem with my FC for a while with the idle adjustment either making the car run at 1500rpm or about 550 Rpm.. with no middle ground. Well today i was fixxing a fuel line and i saw this little adjuster by the airbox and thought hmmmmm... i wonder what this does, so i just started adjusting it until the motor seemed like it was the most happy at a certain spot... (it was running kinda rough before) and now, the idle adjustment screw works perfectly with lots of range of motion, and so i am pretty much happy, i noticed that the throttle response was a million times better, and, that 3500rpm studder, IS COMPLETELY GONE! it feels like it has much more power overall, and pulls really nice, it put a on my face! just felt like posting!