Diesel engines
Turbocharged diesels typically produce strong torque at relatively low engine speeds. Calibration work often focuses on delivery through the mid-range, which is why loaded vans and tow vehicles frequently feel the most obvious difference.
Emissions systems matter here. We retain the systems required for legal road use and do not offer emissions-system deletion, so their condition is part of the suitability assessment.
Petrol engines
Modern turbocharged petrol engines can respond well to calibration, particularly in throttle response and mid-range delivery. Naturally aspirated petrol engines generally have far less headroom, and we will say so rather than overselling the change.
Fuel quality and knock control are more significant considerations on petrol, which affects how conservative a calibration should be.
Which responds better?
For everyday usable torque, turbocharged diesels often show the clearest change. For response and character, turbocharged petrol engines can be rewarding.
Either way, the answer for your vehicle comes from looking at that exact engine and software — not from a general rule.