I did a few searches for my friend on his lopeing idle on his h23...I noticed a bunch of people seem to have this problem.

apparently some say if you recirculate the coolant lines on the thermostat housing for the cold start/FITV that it will lower your temperature on your intake mani...well all it does is give you an idle problem.

if you have a loping idle and you cant locate a vacuum leack or the IACV is ok then check your radiator for bubbles.

I replaced the lines to their respective positions and removed the radiator cap while the engine was running to release the trapped air from the throttle body side of the coolant lines and it idles fine now.

just a heads up for those with idle problems, maybe this is your problem or maybe it is a vacuum leak or IACV, etc.