[SharkBait]

Your engine was starved of oil. No question. It has nothing to do with mods. 75K is nothing and over-modded engines don't fail gradually like this; they fail spectacularly by throwing rods. Unless you heard the rod knock before you had the a accident, it's not just a coincidence that it happened when you first picked it up. You're engine was starved of oil either as result of the accident or by a mistake made during the repair.

Get the accident oil cooler flow tested. If it works, then it was the repair. Someone screwed up. Have the codes scanned independently. If there's nothing there, scan the date (odometer mileage?) for when the codes were last cleared (don't know if that's possible). Don't let them pin it on you. You will need to get agressive with these guys if they won't own up to botching the repair.