without the iac sensor the eec will more then likely go into limp mode. i would highly recommend getting one from the dealer though. parts store sensors are never the same and the reference charts are usually a tad off
I broke mine at the track once and the ECU started to pull a lot of timing after that. Yeah deff get a Ford one, I tried a NAPA one and it sucked balls, ended up going to ford and getting one after.