2011 Equinox 2.4L Ecotec engine. Just purchased from an individual. When I test drove it, it drove fine no issues. Drove it a couple of days, and then it started to stall and die randomly, with no error codes. Cleaned MAF and throttle body, no fix. Found out about the issue with the actuator solenoids so I changed them. While I had it taken apart, I changed spark plugs that were a little carbon fouled. Put everything back, and the issue was still there but worse. It started to die more often. Got a pending P0506 so I cleaned the throttle body and there was no change, so I replaced it, along with the MAF sensor. Ran well for two days, but then today it started to die and now I got the CEL with P0171, a P0131 and a P0137. I really hate to keep throwing parts at it, but at this point I can't seem to find anything else wrong. First it was too rich (P0506) now it's too lean (P0171). I've tried to find vacuum leaks but can't find any so I figured I'd ask before I replace both Oxygen Sensors (which I find weird for both to die at the same time) unless what I'm having is a computer issue. Any thoughts?