I have a 2003 Silverado 2wd with a 5.3. I am getting an engine code of multi cylinder misfire, lean on bank one. I just changed the rear O2 sensor on the bank one side yesterday and it ran a lot better. Any suggestions The plugs on bank one were all fouled and the other bank were fine. The truck was smoking from dumping too much fuel. I checked the pcv value and it appears to be bad (sticking) so I am going to get one in a few minutes.

Check fuel pressure and fuel pressure regulator.
Pull vacuum line of and check for gas in it.
Post back fuel pressure reading engine cranking at idle and on the road.