do you have series plugs or parallell plugs? series plugs as fitted on series engines require a ballast, parallell as found on 90 / 110 engines dont need the ballast. series look like a bent bit of wire on the end of the plug and have a removeable insulator where the cabling terminates, parallell types dont have a removable insulator. first guess is you have parallell types from a newer engine, with the ballast from the older engine.
pictures would help, and ive read threads on this subject elsewhere.
nrg