I just got back from out of town and picked up my 300D with a new (reman.) IP installed. The IP made a considerable difference. I had a pesky fuel leak that wasn't cured by replacing the seals, and an intermittent rough idle when hot. I would also get an occasional sound like an injector nailing. I got sick of messing with it and had Phil hook my up with a reman. IP. The car now idles perfectly smooth at about 550 rpm and has very good power at all rpm. I was really surprised at how much smother the engine feels now. I know these IPs are "never" supposed to fail, but they do apparently wear to the point of affecting performance.

Coincidentally, my AC compressor also ate itself after running 150K miles on 134a. I was never thrilled with the 134a performance, so I had the system restored to R-12. Now I have "real" AC again, feels good. The only problem left seems to be a "sticky" monovalve, because I occasionally get a blast of hot air after the cars has been off for a few minutes (like a fuel stop). The diaphragm looks OK, so I suspect the check valve in the valve body. I'll probably just replace the entire valve.