Maybe check the IAC. That and try cleaning the MAF.

Since the OP didn't say what year the car is, if it's an 04+ then removing the TB and cleaning it along with the MAF might very well solve the issue.

samuelbc- what plugs did you install? Hopefully copper or the stock irridiums... Have you checked the "T" under the SC snout? Often they crack and do not show an issue until moved a bit.