idle dips up and down

Hi, I have a 90 4runner with the 22re and after the engine gets warm the idle dips up and down after a restart. Engine runs fine other than this. Any ideas would be greatly appreciated.
thanks will

I forgot to ad that this truck has been taken great care of has 125000 miles on it, and the top end has been rebuilt, about 5000 miles ago, includding new fuel injectors.