Scott: This is why I hate the MTM+1 chip: a) it is very non-linear (On/Off) and b) everyone I know or have heard of has pinging problems unless they are running 94 octane (or more) fuel. 91 doesn't even come close. I think the chip was designed for 95 RON (not our (RON+MON)/2 crap). Just my observations. Dave F.