I've derestricted like 5 or 6 59i's, after the boss and throttle screw they did a very solid 35 on dead flat, 40 with a slight downhill. Is a 49cc tho, uphill is going to be slow. If you get 28 up a hill that's AWESOME!!! Idk what kind of hill you have around there, in Portland my zuma constantly slows to 25-28 uphill (light mods). The main restriction on the 50i is the throttle body, it's prolly 15mm max! And zombie, it would be some serious work to convert back to carb everything is tied into the fuel injection. Cdi built into the ecu, you would need a new flywheel, carb, cdi.... Not impossible but very deep.