Something strange happend last night - I was driving back from a party and my engine was idling a 2000 rpm (usually 700-1000). On cold starts this is normal but after 30 mins (even highway) it was still reving that high at idle. This morning everything was back to normal (700-1000). Someone can explain this?

I had the oil changed that day and put Lucas Oil Treatment as usual - i don't know
it its related or not...

maybe one of your sensors is going out. mine (st) used to always sit at 2k. this sounds like it may end up like mine was down the road. check the car yourself or pay 60 bucks at a shop to have them fix it. not a prob now but could turn into one. My car now starts at 1.5-2k and then goes to 1k after it warms up. this is no prob to me. warm it starts at 800rpm just like my stock gt does.

Also they may have reset the ecu and your car was just re-adjusting again.

Everythings back to normal - if it happens again ill investigate on the sensors...