well, if it has way too much advanced timing, then if you eliminate a cylinder from the engine, it will speed up due to having one less piston working against the motion of the crankshaft. what is your base timing supposed to be set at? did you check base timing? what is your advance method?(vaccum advance, mechanical, electronic spark timing?) i am sure that you are familliar with these things, but if you set base timing with the advance already on, then you will advance way too much and yes, the motor will work against itself.