The savage engine has more power than the maxx engine but weight and suspension set up will be the deciding factor. You should realize not all Tmaxx's wheelie, even with the 2.5. From what I've seen the 21 conversion is a little heavier and longer, so in order for it to wheelie your suspension will have to be a little on the stiff side. Asisde from suspension and weight there are dozens of other factors like tuning, tires, fuel, surface conditions, etc etc. Also, if the suspension is set up properly for racing and jumping, it shouldnt wheelie at all, after all the suspensions job is to transfer power to the ground in an efficient manner, and wheelies are a waste of power. They are fun, but break alot of parts though.