And I did find out from that same shop, because he located and printed out the schematics of the wiper circuit for me, that the turn indicator/wiper washer switch in the column is definitely different when you have interval wipers so I will need to change the switch in the column. According to the schematics, both ways use the same 4 wires (pink, purple, grey and dark green) and they look like they plug into to main harness the same way either way. That should mean that I don't need to change the main harness. The wiring difference is resolved at the wiper motor. The wiper motor will need to be changed too. They are not the same between interval and non-interval wipers. The interval wiper motor has a circuit board integral with the motor that handles the delay time. Thanks for the added info.