My son has a 2003 that is a bit of a basket case. It is a pieced together truck but that’s not the issue, it recently blew a head gasket. The head gasket was replaced however it is still over pressurizing the cooling system when it gets hot leading me to suspect a head or block crack. It runs but very rough showing codes for rich right and left bank.
before I tear it down to inspect the heads does anyone have any suggestions?

 

whats the mileage ? have the O2 sensors been changed? how long ago were the heads done? did it run good then?