Hello all, I own a 2008 Mitsubishi lancer gts with a 2.0L engine and have recently been having issues with it running lean. It had a p0171 code for awhile and I did a vacuum leak and found a leak coming from the intake tube. So I replaced that yesterday with an upgraded intake and now I am getting P2195 o2 sensor stuck lean code. Also while looking at the fuel trims on my reader, the short term fuel trim is consistently at +25 while idling and drops down when I accelerate. Also to add to the data, I notice my upstream o2 sensor occasionally drops down to 0 volts (not sure if its caused by the leanness or faulty sensor) I checked for vacuum leaks again, replaced spark plugs, and cleaned maf sensor. Does anybody have an idea where the problem might lie?

Thanks