The truth is, they don't have a clue what they are doing. Yes they can be good snake oil salesmen and talk the talk. Yes they can load on to your car a "remap" from some guy the other side of the internet but you must ask yourself a number of questions.
- Is it a £4 bottle of plonk or a £20 bottle?
- How has the file been tested?
- What does the person installing the remap know about cars? Can he perform an initial inspection to ensure there isn't some underlaying issue with the car?
- If it all goes wrong and he bricks the ECU, what is he going to do about it? Does he have the equipment to fix it? Is he simply going to do a runner? Or might he just pass the buck and blame the car. Don't worry if this happens call us, we fix lots of "tuned" cars