Merc 5.0 EFI Running rich

[Gear Lube]

Hello all, Ive been doing the run around with my tbi 5.0 it seems to run well and has good power but then cruising around 1600 rpm and even in neutral at this rpm it dumps raw fuel and when in gear it rolls black smoke out the back. Ive replaced the iac and the cold start sensor. The MAP sensor tested fine. Anyone else battle with these engines?

 

[Gear Lube]

So, I noticed one injector fires heavier than the other. If you swap the wires the heavier fueling also swaps. Also the engine idles with the one heavier fueled side by itself and stalls with the other. Could this be the ECM?