If you replaced with the factory Champion Double Platinum spark plugs, the little welded om platinum alloy discs that make the two ends of the spark gap come off. It takes a magnifying glass to see them.

Some of my mother's 3.3 L second replacement plugs discs came off in only about a year.

I replaced them all with NGK Irridium plugs and so far no failures.
The engine accelerates noticeably smoother.

There is a TSB for 2005 for the 3 "wasted spark" coil packs failing.

EGR valve is all electric and has also failed.
If it fails partially open the engine runs rough.

In your 216,000 miles have you had any AC system freon leaks?
If so, where?