The word is that the repro neutralizer doesn't fix a bad or out of balance engine, I remember years ago when the part was reproduced, the guy that reproduced it was asked if the part actually worked, his reply was he didn't know. Its mostly a matter of what you want to try. If it makes you feel good, do it. I don't personally think that adding weight to the rotating assembly does that much good. I prefer quick throttle response . Adding weight to the rotating assembly slows response. To each his own.