Time to chime in and see who loves them and who hates them. Who sees gains and who thinks they are a waste. State your brand and opinion and whether or not gas mileage has improved or declined.
Personally I have a Group A TBS and love it. I feel the car pulls harder. I am up to speeds in 4th gear that use to be 5th. Still on the first tank of gas..but it is looking real good
will update.... in a few more days!!