Switching them won't work. Have you tried http://www.rockauto.com or http://www.gmotors.com
You're on one.also are there any N* specific forums out there?
So what do they do with the seafoam? Is it to get all the goo and junk out ?I was having the same problem with my 00 deville. It would shut down at the worst times turning around corners etc. I did a seafoam treatment and replaced the iac and haven't had a problem since. I also wasn't getting any codes.