Not every vehicle is ready for tuning out of the box. Part of being a professional tuner is identifying vehicles that need attention before calibration work begins. Sending a file request for a vehicle with underlying issues wastes time for everyone and can damage your reputation.
Vehicles that should be diagnosed first: any vehicle with active warning lights, vehicles with unknown service history, high-mileage vehicles (100,000+ km), vehicles recently purchased from non-specialist sources, N47-equipped vehicles (timing chain), any vehicle showing performance anomalies, and vehicles that have been sitting unused for extended periods.