Working the gas pedal or washing the engine shouldn't have had any effect on the adjustment. BigJim is correct in that as throttle is opened the cable tightens and the farther the pedal is depressed the longer shifting is delayed, but, I drove mine with the TV cable disconnected once (I forgot to reconnect it after rebuilding the transmission) and it upshifted more or less normally, I suspect the TV cable adjustment affects Downshifting more than upshifting.

I would try disconnecting the cable from the throttle and drive it and and see if it still acts the same. If it does, the cable adjustment is not the problem. I'm not even sure your 90 is setup the same as mine, for all I know you may be looking at a cruise control cable. Do you have cruise control?
<img src="/forums/images/graemlins/confused.gif" alt="" />