All the pros lean their motors down to the maximum, please dont be an ass and try to discredit one engines accomplishments over the others.... a person would have to be pretty naive to assume only the guys running GRP engines were willing to lean down enough to get 10 minutes run time.. All pro drivers will be putting the same type of tune on all the other engine brands..if the GRP's had run time advantages they were due to engine design and not some tuning trick........ lean down a motor too far and lose power, the more fuel you burn the more power you make..leaning down past the sweet spot only hurts power and doesn't make them " Scream "