Engine Performance problem
1999 Isuzu Amigo 6 cyl Four Wheel Drive Manual 118,00 miles

My car was serviced recently for high idle ( 2 3 @ rest); shreeks when going from a stop to go; and feels like it lunges forward at a stop (and would go if foot wasnt on the brake).

I had an ?air control valve replaced and then removed because the mechanic said that the replacement didn't make a difference. This mechanic tried everything and couldn't find the problem. His last recommendation was that I take it to a dealer because he thinks that the problem is with the computer system in the car.

I want to know if this type of repair is expensive. I don't think I want to repair it if it is, but there are no other problems that I'm aware of.

Thank you