Take the car out to a road that you can safely test the way the car pulls in second and third gear at WOT
run it up to 3500 RPM at part throttle and then floor the gas pedal, watch the tach and try to pay attention to the way the car feels as it pulls. When the motor quits pulling hard (starts to nose over) try to see what RPM that is, do that in both second and third gear several times to make sure that their close together. Take that information to the track and make several runs shifting at that RPM, once you get several times slips that are close together, within .03 or so, then try shifting the motor 500 RPM lower and after seeing if it likes that or not try 500 RPM higher. Keep testing at different RPM until you find which one is best for your car and combination
When testing at the track look at all of the incremental times, 60 ft.330, 660, 900 or 1000 FT., not just the 1/4 MPH and ET
