Iridium plugs are supposed to come with the gap preset properly for the application. You're not supposed to change it since most standard gap tools can damage the Iridium tip. Yes, you can adjust it, you have to grab the ground electrode with smooth pliers and exercise LOTS of hand control. The AC Delco 41-110 Iridium plugs should be pre-gapped to .040". Even if they were a little tighter, it wouldn't affect it much at all, nothing like what you're experiencing. SES light on? Checked the intake tube for improper reinstallation/leak?
I recently had my battery disconnected for about a month straight, if not more for an engine refresh. Intake manifold was removed and sprayed out with a garden hose, brake cleaner, high-pressure air, etc. TB blade, TB throat and MAF was all cleaned. It fired right up on the first pop and didn't have to relearn idle or anything. It just loped and idled goofy because of the cam and still on the stock tune.
Have you checked the wires to ensure they're all fully snapped into place?