Like VIN7 and I mentioned....the spring rate in the throttle valve affects the pressure rise in the system which affects the shift points. The T.V. system was calibrated with the stock T.V. spring. You replaced the stock spring with a spring with a much higher spring rate. This upsets the T.V. system calibration which affects the shift points. With the higher spring rate...the system thinks the throttle is opened more than it actually is which gives you later shifts. Put the stock T.V. spring back in.