I used a Boyer rev limiter for a couple years and never found it to affect racing results. It was an analog circuit, not digital, and was adjusted by turning a screw, and the running the bike up to see where it cut out. Modern digital systems are much better. I set it a couple hundred rpm higher than my max desired rpm (7200), just for insurance. The only times I ever recall actually hitting that limit were a couple instances during starts, when I wasn't watching the tach, and didn't shift in time. I tried to gear the bike to just reach red line at the end of the fastest straight, so didn't really have any reason to want to over-rev it during the races. The only exception was Daytona, where I deliberately geared the bike a bit high, partly because it was at WOT for so long, but mostly because you could easily pick up a couple hundred rpm running in someone's draft. The Boyer limiter didn't seem to be all that precise, and I eventually quit using it. It was pretty abrupt when it did cut in.
The only other adjustable rev limiter I've used was one I designed and built myself back in the '70s. In prototype form it was about the size of a cereal box, and I hung it on the side of the bike. It worked well, but I only ever got to use it in one race, at Sears Point, and promptly crashed and wiped out that side of the bike, including the rev limiter. It was actually fairly expensive to build, and I decided that building another one wasn't worth the money and effort. It's only real advantage over the Boyer limiter was that I could set the rpm limit very accurately with a set of dip switches. It was also a simple cutoff circuit, with no soft limiting. I had planned to add that after I was sure it worked properly in action.
Lots better digital limiting devices available now, so no point in reinventing the wheel.
Ken