Went to one of the rolling road sessions at Nobles about three years ago (Day Before National Day) with Dingy, and a load of other cars. Ended up as being one of the hottest days of the year, and questioned the operator as to how much bhp we could expect to loose due to the high temps. He told me he could expect particularly the tubo cars to be anything up to 5%. down on the power they expected due to the hight temps. In addition the ecu will retard the ignition when the acts go too high.