2004 Lincoln LS

Good morning. Check engine light is on but not blinking. Engine has low rpm (2500 at idle with pedal fully down) Misfire occurs. My mechanic dried water from coils and plugs, it did not appear to be oil or coolant. He thought I had the engine steam cleaned. After his service the car drove normally until 78 miles then problem reoccured. I did not drive in rain or snow but the moisture reappears around the coil and plugs with check engine light on. The misfire may have killed the catalytic convertor but thats another chapter.
This is the third time he's dried the coils & plugs but he needs to firgure the source of the water and that's my question.

Also will new boots or gaskets in the wells solve the problem?
I'd be happy to give you a nice bonus if you come up with the correct solution. If you do, I think there will be a number of other probelms you can help me with.