I had a revelation when I woke up this morning. What if... just what if the problem with the C4 feeling that it is down a couple of cylinders is because it really is? So I go down and pop the hood and, even in my morning haze, notice two scorched and cracked plug wires. It's now running like a few thousand bucks again.
Thank you all for your sympathies/help, though. At least it now only needs bushings, a clutch, and a shitton of other stuff.