Without opening the file: Did the seller provide a data sheet? Lambda logs? A dyno graph with AFR?
Opening the file in WinOLS: Compare against stock. Check: rail pressure, SOI, smoke limiter, quantity maps, torque limiters. A file where only rail pressure and quantity changed is suspicious.
The lambda check: After fitting: wideband sensor, hard pull 2,000–4,000 rpm. Lambda below 1.2 on diesel at full load = fueling issue.
In Diesel Practice, one of the exercises is analyzing a purchased Stage 1 file and identifying what was changed and what was missed.