Ford Focus running rough

A Ford Focus 1.8tdci was brought to us for running rough. During a test drive, we observed a significant power loss between 1,000 and 3,000 rpm, followed by a slow increase in power. We also noticed that the temperature gauge did not exceed 70°C, prompting us to return to base. Upon inspecting the vehicle, we found that there was enough coolant but the radiator hose was excessively pressurized, indicating a potential head gasket failure. After letting the engine cool, we removed the radiator cap and ran a sniff test, which confirmed our suspicion. We then proceeded to repair the head gasket, restoring normal cooling system functionality.
After letting the engine reach operating temperature, we went for another test drive, but the car still lacked low-end power. However, it performed exceptionally well above 3,000 rpm, which led us to conclude that the car had a poor map for road use. We used AlientTech to remap the car with our stage 1 tuned files, which resulted in a 30bhp and 70nm torque gain from a standard stock file. This upgrade ensured that the car now runs smoothly and has a consistent power delivery throughout the rev range without damaging the engine.