Well I'll go back to what I said before...
Swap in a NON-adjustable OEM fuel pressure regulator to eliminate it as a suspect... chasing multiple gremlins at once sucks.
It definetely sounds like your Mass Air Transfer table is hosed. Code 42-Fuel mixture rich... The EEC is trying to pull as much fuel as possible OUT of the mixture (i.e. leaning it out as much as possible). That would certainly explain the symptoms you describe.
Once again though.... Try and eliminate one problem/suspect at a time vs. shotgun mx on them all.
