2001 Monte Carlo SS that is throwing codes P0171 fuel trim system lean bank 1 and P0131 circuit low voltage bank 1 sensor 1. All this started after I pressure washed the engine and added seafoam treatment to the gas tank and crankcase. When the check engine light came on I had a scan done and they told me that the code is usually the 02 sensor..so I replaced both O2 sensors. Still it came right back and the car has a very rough start..and at times takes 30 seconds to start and when it does it idles so rough it sounds like it's knocking and often stalls. After a min or so it smooths out but at times it will run but the gas pedal almost doesn't respond and it feels like the car is gonna stall. I cleaned the mass air meter and that did help but it still has hard starting and has trouble restarting if I cut it off. I have dash command 0bd2 reader and have recorded several episodes of this but don't know how to make heads or tails of dash command readings. I have run out the tank of fuel that had the seafoam in it and am halfway though a new tank of 93 octane and it still throwing the codes when I clear them and has the same issues. Any advise on what I should check now that I have replaced the 02 and cleaned the mass air???