2001 sc2 w/ a high idle

[Mean Green SC2]

its a 2001 sc2 5spd with 63k miles.

it idles great most of the time, right at ~900, but sometimes after driving a while, on the highway or in town, it will idle high. the idle is usually exactly 1500, and it will go away if i turn the car off then back on. sometimes if i turn the ac on to force the fan on, leave it on minute and turn the ac off, when the fan goes off the idle will drop to normal. my gf had the car since new and says its always idled high like that sometimes.

sometimes when i start it up in the morning it will soar to ~2500 and will soon drop to ~1500, and it can again be fixed by just turning the car off then back on.

the temp usually stays a hair above 1/4, but if i am in traffic with the ac off, it will sometimes go to about 1/2 until i start moving. which i have read is normal.

the car has never been touched, except for dealer oil changes, a dealer tuneup at 30k, and i just changed plugs, wires, pcv, and air filter to a kandn drop in, at 60k. i took the neg battery cable off for about 1/2 an hour, just in case the car needed to get used to the kandn. i use reg 87 oct gas.

something else that may be related, is it also feels like sometimes i feel the slightest buck or hesitation when accerating in 1st, 2nd, or 3rd. i cant tell if its just the responsive gas pedal of a saturn or something i should look at. the other night on a 2hr drive with cruise set on 80, i definately felt it jerk a few times. first i thought it was from getting pushed around when i would pass a big truck or 18 wheeler, but it also did it once or twice when nothing was around. but, it hasnt done it since.

from reading posts on here, i am going to start with changing the coolant temp sensor, cleaning the tb and iac, and checking for cracked vac hoses. anything else i should look at?