after a run in my 25ol sometimes it dont idol down all the way? about 1300 rpms? if i goose it while its in neutral it will drop down to normal? any guesses?

iac valve ,,will do that

+1 could be sticking or malfunctioning IAC.

+2 IAC. Remember you have to put the engine in "service mode" for the new part to self calibrate. You can't just stick it on. (at least thats true on my 97 gen VI 502)

ok so now where do i get one? on the merc site it says not a servicable part? looks like you have to buy whole tb! i got mine out and it has a part number 208710810a. and also how do i put it in service mode?

It's around $100 at the dealer. You either use the scan tool or you can jump it into service mode using a paper clip. Find an old schooler Merc guy to walk you thru that. I'm not going to post that info here and get flamed.

I didn't have to put my 99 454 mag mpi into service mode..

just plugged in and worked.