is there anyway I can force my 4.2 SC to just run its base map? Without unplugging the maf cause that throws all the errors in the world.

I have a theory that my exhaust manifold is leaking. which making the sensor think its lean, so it adds more fuel to burn, which is leaving a ton of unburnt fuel going to the cats and heating them up.

Normally manifests when am cruising on the motorway at a consistent speed for a while, I get Cat Efficiency codes.

So if I can run a base map for a bit to diagnose, it should be fine.