the screw on the TB is just a blade stop. the computer will just adjust the IAC to compensate for what ever you did the the set screw until the diff is too much.. then it will set the SES.

like said you need a tuner to adjust the idle. so DHP or HPtuners.

OP is there a reason you want or need to adjust the idle? maybe we can figure out another solution or help fix what is wrong.