STFTs in Fords aren't the same as GM. In GM computers, STFTs are the short term fuel corrections in %, while on Fords they are that and are also the commanded lambda, called lambse.
Think of lambse as a commanded lambda which includes the fuel correction from the hegos (O2). The KAMRF's are closer to what STFTs are in GM jargon.

I think P1151 in Ford is for a lean condition which can't be corrected adding fuel.
Without going into much detail, you can see if the afr is rich or lean watching the O2 volts. If they go above 600 for long periods of time, it means you have a rich condition. If the volts peg below 300 then it's a lean condition.
Swap O2 sensors from side to side and retest. If you get the same results, swap injectors from bank to bank. If the problem follows the injectors there is a problem with one of them (or more). If the problem remains in the same bank, check your plugs, coils, cables and test for vacuum leaks.