I agree with troughy to a point. Custom tuning is by far better than running your car with the standard maps, however, it's not mandatory. The standard tunes in the flasher are relatively conservative. They would have to be, as the the suppliers know that the cars being flashed are all going to be different. Basically, what ford does at the factory floor but at a slightly higher state of tune. This not only leaves room for the differences in each car/engine, but also leaves scope for custom tuners to extract the best out of our cars. I ran the standard 10PSI map in my car for 6+ months. The car was fine, went much better than standard, and was never in danger due to poor AFR's or pinging. The only precaution I would suggest as mandatory, is a dyno run of the car before and after flashing. This will assure the owner of AFR's etc. Basic differences between standard map and custom tune? The custom tune is smoother and gives me more power.