check the cold start plunger. If it isn't seating properly is will cause idle problems.
Bingo - this is what causes this 9 out of 10 times -
the hot start will have corrosion due to a not so great oem plastic fitting - keeping it from seating correctly. You have to clean this periodically and use some lithium grease in there.
ZipTy Racing makes a nice metal fitting to help alleviate this - periodic cleaning is key