Need Help

I have an 88 Chrysler New Yorker with a 3.0 As soon as it warms up a little and I drop it in gear the idle goes up to about 3000 rpm’s. Replaced the IAC valve. Still does the high idle when dropped into gear. No vacuum leaks. MAP sensor is good. What else could cause the high idle when dropped into gear? I need some other direction to look in for the problem. Any help? Anything at all?

did you read any stored trouble codes?