The reason why it is better for you with the map unhooked is because it trips the computer into maf only made, and when it does that, it reverts to the base look up tables including the base fuel tables. You presumably have a stockish truck, so the tables it references are pretty bag on when it defaults to base calculations. If you plug the map in with a signal problem, it will assume the hooked up reading is correct.
Most people give these computers too much credit. They dont understand common sense.
Most people give these computers too much credit. They dont understand common sense.