My Pinto 2.0l has some cruddy looking plugs which are overdue a change I think.They are NGK R APR6FS. However...Haynes manual states Autolite BF32. Some websites I have checked suggest AP6F VG. NE1 know the correct one I should use? Engine is unmodded, and runs on single weber, with unleaded fuel plus castrol additive - (the one with octane booster) TYIA