They are a gimmick. Nothing but a fancy wandering light to amaze your friends with. I have one.
The Autometer. They are not accurate enough to depend on.
My friends coupe has one. We were experimenting with nitrous jets at the track. It read in the rich the whole way down the track. At the pits he had little specks of aluminum on his plugs!!!!
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1988 Mustang GT
11.8 @ 123 (7/14/01)
1992 BadAzz Wrangler
1993 Explorer
See my car at:
www.mustangworks.com/cgi-bin/moi-display.cgi?179