I was a serious competitor back then, and never used one. Conservative needle settings on the ground are all that's needed. If there is a problem in-flight (like the fuel tubing springs a leak, making the engine lean out) just kill the engine and come in. I never thought the extra complexity was worth it.

However, they do work well. For those who renmember the NorthEast crew, Art, Lance & Jeff used them on their EU1-As