Feeler for what you guys think before starting a build

[aal219]

I recently purchased a dirt cheap '01 L.L. Bean Outback for a flat 6 swap I plan to do to my flat 4 car and noticed that the car was in diagnostic mode (green connectors plugged together) when I towed it away. Previous owner claims he was driving it like this for a year (no, not a typo).

 

How much damage do you guys think it did to that motor? It starts fine, runs strong (no misfire), and doesn't throw any check engine lights (when it's not plugged in diagnostic mode).

 

My plan is to do an oil pressure test, compression and leakdown test, and send in an oil sample before I decide how much re-building this engine will need to be reliable (at least 100k of use before it needs to come out again).

 

Any input would be appreciated; thanks!