Depends on the cam you are running, very mild and you will probably never notice the differance, even a dyno would have a hard time telling the differance, if you are running a big cam you will probably notice more differance, if you are running a very agressive flat tappet with mopar specific lobes I would conside it a must have. A lifter bore a degree or two out can keep the lifter from rotateing or cause the lobe to hit the side of the lifter, either way can flatten a lobe real quick. If you are reuseing a cam and lifters that was already in the engine it could also cause the lobes to go flat as they were broken in already with the wrong angles and now being corrected could cause more issues, sort of like mixing up the lifters.