The oil found on the injectors could be blow by, take the hose off the valve cover or remove the oil cap at idle, is there lots of pressure? If so bingo, could be rings, could be valves, could be timing but yes internal NOT injection pump issues. For example the oil cap should stay put once unthreaded, not fly off from pressure. If there is not a ton of blowby look at the injection system, maybe chain timing, start of injection timing, lack of pressure. A good pump recalibration costs money but really can refresh performance on an older engine, it was night and day on two of our cars (that had everything else checked out).
I would figure it out before swapping engines, then you know what parts are good in the future even if you decide to swap in the end. Compression does not tell much of the story, sure it can tell you when it is worn out (a drive will usually tell you that, or hard to start!) but little else. The timing and pressure of the injection pump is probably a key here.
Possibly the cam timing could be off since the head work too...thinking aloud maybe the keyway is drifting (seen it on VWs often after work). Chain could be too loose and skipped time, of course at this age and mileage it could be anything!