Bad gas mileage LS swap

[sixtoes1313]

UPDATE: I actually ran across a great deal on gearvendors unit on this site...so I picked it up. Still haven't installed it. Lately I've been noticing the car running rougher than usual. It'll be more hesitant to start, have some flat spots in the 2-3500rpm range, and stall when rapidly decelerating. I'm beginning to think the car is running in an open loop setting. Reason I say this is one day I was messing with my intake, unplugged the MAF and forgot to plug it back in. Car started normally and drove around no different for a week before I realized it was unplugged. There is no difference between when the MAF is plugged in or unplugged. I suspected a bad MAF- aquired a new one...and problem is the same. MAF, and 02's are reading well on the data pids, but o'2 have a very constant fluctuation...almost no "normal" unperfect variations. Any idea why this would be occuring? I would think that if the PCM is running open loop(off pre programmed tables) it would explain why the tune wouldn't be as good as it once was, as well as all the other abnormalities. Could my Alternator being unplugged from the PCM have anything to do with it? (never got the correct truck connector- charges fine at like 12.7v not great but good enough) no other CEL's