Got this 2002 chevy venture with 202k Miles about a month ago because it had a brand new transmission and the motor and body of van were pretty damn decent for the age and mileage and when I bought the van it was pulling a code for P0135 and P0128, so I tore the bad 02 sensor out for bank 1 sensor 1 and replaced the thermostat and 02 sensor while I was doing that we replaced the intake gaskets for the entire intake lower and upper since they were leaky we replaced a couple original hoses that were severely rotted away also, we got everything back together and the original codes went away but now it was misfiring really bad and had a whole new set of codes reading at P0304 cylinder 4 misfire, got all new spark plugs, wires and cleaned the dirty injectors and tested that they all fire correctly and they did we replaced the fuel pressure regulator so we put it all back together again and now the cylinder 4 misfire code is gone and now it's pulling a couple of new codes and the old ones are gone the new ones now are P0131 02 sensor low voltage and P0300 random misfire the engine is rocking like it is trying to jump out ! It idles rough but drives fine and if left idling for 2 minutes or more over heats it stalled out while test driving and idling at red light and I can't figure this out I don't have any ideas so again I have replaced
Spark plugs
Wires
Intake gaskets
Thermostat
Heater hoses
Fuel pressure regulator
Starter relay
02 sensor
Cleaned the injectors and made sure they all work

Please help

 

Thinking the cat.