From what I've seen, you will lose about a couple of miles per gallon in fuel saving. But at this point, Honda is no longer covering any TSBs for the work. There is a software update that would be applied to the computer, which is supposedly the fix. When my engine started flipping out at about 70k miles because of the VCM issue, Honda replaced rings, plugs, and some other stuff (can't remember exactly) and reprogrammed the computer. I'm now at 213k miles with no SVCM or Muzzler, so I guess the reprogramming worked.