I have a BBC Top Dragster drag race application with a 2 step. From the release of the transbrake and 2 step to when it sits on the converter takes approximately .40 seconds. I get a lean spike in that transition at about .20 seconds after the transbrake releases. I see it with the FAST wideband and a secondary Dayton sensor system I data log through the fast system analog channel. Is it truly a lean spike or does or is it still recovering from the unburned A/F mixture on the 2step? Wondering if anyone knows how fast these sensors actually react.