My 88" petrol S2A is "bucking" art high throttle settings under load. It's as if you floor the accelerator and let off, and floor it again, then let off and then again full throttle. Eventually if I don't let off the gas it will stall. Letting off the gas will temporarily correct the bucking but by that time I have lost momentum and must start in 1st gear again. It is also sputtering at idle. I have replaced the carburetor, fuel pump, fuel filter and installed an electric auxiliary fuel pump as well. My mechanic says I need a new distributor because it doesn't hold correct dwell. Would a new distributor help? Or, is my problem fuel starvation?