That's because they are running methanol with AFR's as rich as 3:1. It's the inlet temps which bring on detonation, higher intake temps, detonation is more likely to occur. The cooler the charge the more timing advance you can add to the map. It's the low compression of these engines which keep them "safe" I would go with an fmic, you won't regret it and for the same price as an arc tmic, you then have the chance to plan for the future if you need to without having the hassle to sell and buy again. The zisco one looks good with very little cutting.