EGT's rise with lower octane ratings and the ecu richens up the charge to lower them back down again, which retards the timing further and restricts boost. Whether I had a bit of contamination in my tank, or these Nitro+ additives don't agree with my highly strung map I don't know. Time will tell. It hasn't ever done it even after repeated WOT pulls through all gears; I have taken it at WOT from 50mph to 155 in one go previously and it didn't back off once. And nor did it in the rolling road.