Yeah, trying to make the stock DME work with forced injection is difficult, not impossible. You'd replace the AFM with a MAF that can measure the extra flow. Then squeeze the entire stock fuel-map down into 1/2 the data-cells on the chips. Then program the empty space with fuel-values for boost.
FWIW, the ROW fuel-maps are much leaner, -5 to -10% less fuel than the USA maps across the board. These are actually more precise mappings that matches actual air-flow volumes. The USA cars rely on the O2-sensor to pull back the fuel into proper stoich. ranges.
The main reason the European cars had more HP was due to the higher-compression pistons, and a lesser amount from having no catalytic. If you want quick easy HP, just swap in a set of Euro 10.6:1 pistons.
The trick with increasing HP is to flow more air through the engine, not ffuel. It's the numbers of oxygen molecules per intake-stroke that counts, you can always dump in more and more fuel, but once you have enough fuel to mix and burn with each oxygen, that's the maximum amount of power you're gonna make. Extra fuel will have no oxygen to burn with and will go out the tail pipe as pure hydrocarbons.
Remember that hot-rod saying from the '60s???