[Karl]

I've seen them and wondered about them.
The vacuum gauge seems a cheaper and I suspect just as good an alternative .
I can understand the Brit guys liking them. My Father used to say he had never worked on an British car that was easy to tune-He believed that the Brits struggled to get the carburation right on their engines (and I own a 1967 Sunbeam Alpine- Twin Stromberg 150CDs-ugh !! )