Cleaning them works for driving conditions but that motor has to react faster to the situation when goosing the gas and should probably be replaced... It's probably working, just not fast enough...
I had the same problem recently and it turned out to be a dirty MAF sensor, inspect it and spray it off with some brake cleaner and that may solve the problem!
[addsig]
its youre iac....be sure to replace with a factory unit. autozone and all them are not good. www.texas mustangs.com has them and they are factory replacements