Ahhh, I would say YES the new oil pump is the cause.. They are dumping a LOT more oil in to avoid any bearing issues. And the idling around coupled with the new oil pump would help to load it up a bit... There will be no adverse affect from running the hotter plugs if the engine is stock, if you've gotten any mods such as Hydro-tecs rec heads you will want to stay with the colder plug, doing just reeds won't change the compression any so you could run the hotter plug with them.. I'd be willing to bet if you put the NGK #5's in your problem would go away... It is also possible that your oil pump rod is not adjusted properly, may want to have that checked too...