I vote Jammin JPX .... Tho I fully believe Mark's modded N21 would be a killer engine no doupt..... However IMO the Picco/Jammin's have the most torque of any of the .21's, which really works well in Truggy, especially if your running with some traction..... I have run and modified all sorts of engines and myself have no issue making a S3 run with a jammin down the straight... However no matter what I do its difficult if not impossible to make a S3 have the same snap and launch as the JPX.... In fact I have not found another .21 that has the same type of bottom end the JPX has.... The JPX does scream hard on top, but there are faster out there, however IMO nothing has the same sort of acceleration potential the Jammin has.... The more load you put on the Jammin the more it will separate itself from the other .21's...... It works excelent in a truggy and will make your machine feel very light and effortless.... I have seen plenty of .21's that are just as fast, but I haven't found another with the same kind of power the Jammin/Picco has.......No knock against Mark's work by any means, but when it comes to a truggy engine I am always going to pick the Picco over any others.....Even if it was my own modded N21 I would still pick the Picco....