I tried unplugging the iac valve to lower the idle. After doing so the idle went above 1200rpms and stayed there. My mileage went down. So thinking I had unplugged something that was not the IAC. I unplugged the EGR valve. The car immediately threw p0405(egr voltage low). I assumed this was the iac because the idle was dropping about 50rpms below what it was. Well I drove the car last night for the first time on the highway. Steady state cruise was 77mpg @50mph!. I had a complete highway segment of 13 miles at 55mph that went 62mpg while not paying attention or even trying. Last night was the first time on the highway with a hot car and had not noticed the increased mileage. I'm wondering now if the scangauge has been fooled. If I spent more time on the highway I could test this but unfortunately I'm nearly 100% city since I'm attending a church thats closer to me now.
02 Saturn SL
for pics click the link below
I, too, unplugged what I thought was the IAC valve while the engine was on and the idle went up. It threw a code and if I remember correctly it was something about the IAC. I haven't had a chance to mess with it since then.