[Blown353]

I haven't dealt with a Gen 6, but at 5500 feet you will probably need to richen the entire map about 30-35% and also add a several of degrees of timing in all the cruise areas to make up for lost combustion efficiency. It will probably want a bit more timing under boost.

I know it seems counter-intuitive to richen the map as the car is now at a higher altitude; common sense and carb experience says that as altitude goes up air density decreases and thus the mixture gets richer and you need to lean it out.

However, with an ECU that doesn't have barometric pressure compensation such as your Gen 6, the prevailing "standard" pressure at startup will drop from ~100 kPa at sea level (where the car was) to probably about 80-85 kPa at 5500'; this moves the tune into a lighter load and thus leaner area of the tune than it would be at sea level so the car will be lean all the time.