The 2000 thru 2003 4.2L has a TSB about the isolator bolts securing the plastic plenium chamber leaking causing the two codes. Its a pricey fix, about $150.00 for the parts. Takes a good 2-3 hours to do. Its not hard, just awkward to get at some of the crap. Note, the firewall sound deadener nees to be cut by the heater hoses for more clearance. Give me a PM if interested in more info.
Good old Bill