There's a couple reasons for it, (we have discussed about it before on a previous thread too if you want to have a look at what was said) - CAI generally freaks the ECU out for the first couple of minutes, generally as Northy would suggest too is to reset your ECU anyway. - Temperature wise, never had my temp bar go beyond halfway even on a VERY hot day at the track, besides, the temp gauge on our car suck anyway, not very accurate (shao will back me up on this one) - ECU / Aircond, as i have personally discovered is that when the weather is pretty hot, and you had the A/C on and then when you sit the car at the lights or restart it from a slight stop, the idle would once in a while bounce up and down. I have discovered that the ECU or something seems to upset the idle ESPECIALLY when the A/C is turned OFF. Blip the throttle, once if not a couple of times... it always works for me. also, after hard driving, please don't just stop your car. Be nice to it, do a couple laps around the block slowly and blip the throttle before killing it, that'll help you start easier the next morning! cheers.