this device may help, it activates various modes that were available from factory (including idle up) but are no longer available in your not so professional swap
https://all4swap.ru/product/mpx-fan
Cel is connected to ecu pin W, active low. Wire an extra small bulb or led and see if it works. It may not work because of ecu aging or other problems that you should expect in 30 year old car
https://all4swap.ru/product/atemu
You can have zero codes, but without this one your vvti will work in limited (failsafe) range, seriously limiting torque and power