Full systems use a header that is larger than the stock unit. More volume passing through. Whomever said they got better gains from a stock header and slip-ons probably rides unicorns in their spare time.
The full system map is designed to adjust fueling based on the larger volume flowing through the larger diameter headers. Using the stock header with a "full system" map is going to over fuel things. The best result with anything is using the map as a based then having it fine tuned either by a shop or by using an autotune feature with which ever fuel enhancer you've purchased.
Both Bazzaz and Dyno Jet have these autotune features.
The full system map is designed to adjust fueling based on the larger volume flowing through the larger diameter headers. Using the stock header with a "full system" map is going to over fuel things. The best result with anything is using the map as a based then having it fine tuned either by a shop or by using an autotune feature with which ever fuel enhancer you've purchased.
Both Bazzaz and Dyno Jet have these autotune features.