Stumbling of engine at low cruising speeds between 30-50mph

I did the plugs because I was replacing the COP's, so I wanted to prevent having to remove them a second time. One of the COP's had gotten wet (accidentally, I was washing the engine) and was misfiring, caused a blinking CEL and wouldn't stop misfiring. The IAC was replaced because of the notorious "howl" that progressed to a stuck IAC.. Replaced the DPFE because that was suggested by a mechanic as where the issue might be occurring - it did have a small pinhole burned through it. Replaced the TPS just out of good measure, because I had taken off the throttle body and cleaned it, carb cleaner got into it and figured that might make it fail, and it was cheap. Yeah I agree it's not wise to install a lot of parts, but car has a lot of electrical dry rot. The EGR could be sticking, I really need to have it replaced just because of age. No, there's not been a compression test - I'll be doing that when I have free time and the weather is warmer. It doesn't burn any oil though, so not too worried about compression right now. The coolant leak suggestion - #4 was dry when I put the plugs in, and it's not losing any antifreeze - but I'll look again just in case..