That a good question I'm hoping Wayne from LET would chime in. He has the graph and Dyno run. Car has a 181 pulley so I would guess 18lbs boost. I had gauges in the last 3 cars I built and this time my wife said she didn't want any, Sooo I don't have any. Good thing was car went lean near end of rpms so I know there is no belt slippage. I picked up 13-15hp from the tuning but the throttle responce and performance on the ride home was awsome. Anytime between 45-55 you would half throttle it, it would spin the rears.