I have not raced before and did'nt take into consideration running time I take it 28's are just too greedy on fuel for the track. I do want to get into racing but if I did I would want a competative car capable of winning races. Ive seen Hyper ST Pro's with diffs from the Kyosho ST and chassis stiffners from the Kyosho aswell and fitted with different tanks. Are these mods esential or just preferance. As I was going to go with my Hyper completely original with the Axial 32 and a JP tuned pipe. But I am now thinking maybe I should start looking at the most powerfull 21 I can get my hands on. I tried it with my old thunder tiger pro 21 R engine and it was better than the Mac 28 much more lively at mid range and great top power supposed to be very similar to the OS 21RZ engine but my Carb kept coming lose. I then looked on youtube wow some of these 21's really are fast seen an RB, Ninja and a Picco and have to admit they really are something else compared to the cheaper engines. Are the Sirio engines up there with the top engines also are the 28's a waste of time as the engine size is a good increase I would have thought the extra torque through the band would be noticeable.