Morrey-
I don't foil ribs. I've been cooking them the same way for years, and they always come out great, so I don't really tinker with the method much. Here's what I do:
- I get two-packs of spares at Costco, usually 4-4.5 lbs per rack
- I trim the ribs to St Louis cut, remove membrane, etc.
- I put a light mustard slather on each side, and apply the amount of rub I'm in the mood for
- If there's room, I'll cook flat at 230 top grate temp (240 lid for me) for about 6 hours, if not enough room, I use a rib rack
- I'll check for tenderness starting at about 5.5 hours, but it almost always takes 6 to 6.5 hours
- I don't spritz at all, and I save saucing for each person to do to their taste on the plate
I definitely notice a spike in temp as you do when I remove the lid, and, as you surmised, that's due to the increase in airflow with the lid off. I find that things settle down pretty quickly. With my first Guru run, I wasn't using a clay saucer for a heat sink (just ran an empty foiled pan), so the temps spiked up longer for me than I think they would have when I removed the lid to check for tenderness.
Sorry for being long winded!
R