If I had to do it again my RB C6 L2G/ pipe combo would be what I would purchase again, with a decent tune I can go at least 7.5 minutes. I haven't timed a full tank on a near perfect tune.
It has more than enough low and top end, at the RC pro in STL my weight seemed a bit more in my XT8 than alot of others and I did not see anyone that had more motor. If in fact they did they could not put it to use. The only other motor I have driven in a truggy is another guys XT8 with a LRP .28 and the low end was nothing near what I have, even after seriously tuning on it.
Fuel mileage is key in any racing, and I feel that a good tuned .21 is the way to go for serious competition. Just my opinion....