I have tried a new IAC which helped a little bit and found and fixed a crack in a pcv hose. The car doesn't seem as peppy as i would think it should be but it shifts ok to what i can tell with out a tach. The biggest issue i have is when i drive then go and put the car back in park. When shifting into park the car increases idle as it should but then doesn't go back down. it stays at a high idle until i turn the car off. Is my Throttle position sensor bad and preventing it in any way? I looked at the TPS plug and the pins have a little of this white corrosion on them. I tried to clean it with some electrical connection cleaner but i dont think it helped. is it hard to replace the TPS?