Have a Mitzu with a nissan engine, NIKKI Regulator, everything is just like in the newer nissan's and cats. Engine rpm surges at times when you step on the throttle hard, if you ease into it it will rev fine and if you put a load on it(Tilt Bypass) it still runs fine,at times. Is intermitant,talked with one of our other service techs that works on alot of nissans and he mentioned maybe the MAF sensor or the injector,swapped out MAF on a truck that was running good,still acted up at times,replaced injector,still acted up so replaced MAF with a good one, Removed coils and checked resistance on all and all are the same resistance. Drained a little bit out of regulator when i first checked out truck, only has 1040 hrs on it and no codes or lights saying anythings wrong. Did think that maybe the wires to the plugs were shorting to the head as there was alot of dust packed around the base of the plug,blew out and tried again and ran good till running it up on a incline then would start surging again, this truck is in a feed mill and see's some really fine dust, air filter gets blown out on a regular basis.
Anyone have any other ideas, going to pull the plugs in the morning after it has cooled overnight and replace them, acts like an old governed engine would if the governor was out of adjustment.