Hi,
My TT .15 has 4 "needles". Needle valve, screw holding throttle arm on, vertical screw that seems to set low idle throttle barrel end stop (?) and a vertical "needle" screw that ??????????

Can someone explain these two "needles" or screws?

Engine is fairly new. Runs OK but won't idle down for landing. Full off throttle still pulls A/C along at landing speeds. Right after landing the engine quits. I'm afraid to idle it down anymore. Afraid it will quit in the air and land short. Just seems like low idle throttle setting needs fuel/air adjustment. But how?

Bill