I think it's one of those things that you just have to gain experience and play with to see what works best for you. Although I'm happy with the 5.5T motor in my Mini Truggy right now, the track is a large 1/8 track that has been shortened to run 1/10 classes (the large triple on the back section of the 1/8 track is closed off) so the wide lanes and hard pack surface make it suitable for the 5.5T motor, though I admit that the truck tends to wheelie in some sections to where I have to be a little more smoother on the throttle which can hurt my lap times when I have to back off the throttle to get all 4 wheels on the dirt... I might drop in a 6.5T motor soon which might give me faster lap times even though it might be slower down the straight and I think that's where boost comes into play which I haven't mastered yet. I just went down on my center diff to try this weekend to see if that helps prevent the wheelies, if that doesn't work then a 6.5T motor may be the ticket, at least I'm not thermaling, ha!