My engine hunts pretty bad since I put intercooler. I brought the car to many workshop but no one had clear idea on a problem.
Then I found there is extra injector controller hooked to ECU. I unplugged the controller and engine stopped hunting but engine check light on a dash came on.... if I connect the controller, engine check light is off but engine hunts again.
If it is a 4A-GZE and it has factory computer
you have an air leak check the cooler and all pipes and fittings
I Would also guess it is map sensor.
I Am assuming a lot but its my guess.
MATT.