I have several times used WEP when in a dogfight. I try to engage it for a min or 2 maybe, then turn off and cycle it that way with a little time in between uses. I find that eventually my engine powers back (not by my doing) and will no longer allow acceleration and runs at some reduced setting of power. My assumption is I have damaged the engine. But I just noticed the last time this happened that the HUD indicates that the engine, cooling etc are all at 100%. Is this some function of stalling or just that the HUD indicators are simply wrong? Any advice is welcome. I am using Medium as my model for flight. Thank you.

I've seen this before, but haven't put much time into it. I did map the radiator control to the stick to see if that had something to do with it...

Make sure you are adjusting mixture or set it to auto in workshops.

Thank you however Auto mixture is on, as is auto prop etc.

OK possibly you are using it too quickly with too short a time in-between.

Thank you. I assume it was WEP related, although HUD showed all systems at 100% working correctly.

Just to further the mystery, on a mission where I returned to the home field early as I had used up all my ammunition, was not hit by any enemy planes, didn't use WEP, and engine was running normally, I went into 10% nose down dive to lose altitude, with the engine at idle, and when I came to level up the engine would not spool up at all. had to land in a field, hit a fence which destroyed the aircraft and at the debrief screen was told I was shot down.

Just an FYI.

Too lean mixture?
EDIT: Oh, you said it is set to AUTO.

Maybe you got hit by something else, friendly flak, also there are engine failures modelled.
Check joystick / throttle mappings aren't clashing somewhere too.