Where to start?

[Tone]

Check fuel pressure with a gauge before spending $50 on a regulator. Post the exact codes and we can help you better - intake gaskets failing typically cause irratic idle high and low for no apparent reason and could cause stalling. Intake gasket issue usually shows at least a lean condition - use the search feature to find codes usually thrown. O2 sensors from Isuzu only cost $100 ea and the Bosch aftermarket ones work fine and are around $65.

Cats will start to rattle when they are coming apart and I would definitely go with aftermarket replacements for those at less than $200 each plus a little labor to weld them in.

[mbeach]

This comes from Bob in response to a similar Q:

Sounds like a Vacumn leak to me. Make a good visual - CK PVC at valve & rear of Plenum also EGR connection at back of Plenum also Vacumn line at throttle body and at fuel regulator (Fuel rails Driver side rear).If all else fails spray Carb cleaner with engine running at intake manifold gasket mating services if RPM rises Try tightening manifold, if that fails new Intake Gaskets req. order
PN 8-97237-538-0 two req at $18 + each - 1-800- 727-8066 ask for Merlin. S&H is free

Torque value is 13 FT LBS on all intake manifold nuts & Cap Screws.

I had a similar surging upon hot starts and found it to be a vacuum leak at the intake manifold gasket. Just to make sure, I stuck a length of 3/8 hose im my ear and used it as a stethoscope to find the exact point of (air) entry.
Depending on your VX's in service date, this should be a warranty fix.

As for the cat, a 'rattling heatshield sound' can come from INSIDE the catalytic convertor body (as Tone mentioned), this usually happens after the matrix has been blown out and the internal shielding no longer has any material to keep it in place.
Get your in/out pipe diameter and overall length then order an aftermarket (high flow) replacement cat for <$125. I'm a big fan of Random Technologies' units. Have it welded in for $20. Catco units also come highly recommended, but I have no experience with them.

It's easy to get frustrated when so many things are going wrong with your truck, but when you look at the root cause of these failures, they all point to one, easily repaired problem.
Bad intake manifold gasket(s) = lean fuel/air mix (weird idle and CELs 017x),
Lean fuel/air mix = hot combustion temps,
Hot combustion = hot exhaust gas temps,
Hot EGTs = burnt O2 sensor(s) (and CELs again),
Burnt O2 sensors = burnt catalytic convertor,
crumbling cat = rattling noises.

Best of luck and keep your chin up, this board's value lies in its collective experiences with these same troubles.

Edit: I just noticed that you had an Injen intake. I don't know about the VX for sure, but there have been troubles with aftermarket CAIs on quite a few other vehicles. They cause the engine to run lean, even beyond what the ECM and fuel injectors are capable of managing. Just a thought.

[dohvb1]

Ok got it scanned again today. This time two codes.

PO101 MAF System Performance

PO140 H02S Circuit No Activity Bank 1 Sensor 2

I'll try and check for a intake manifold leak later today.

Thanks for Random Technology suggestion. Find them on for sale on the web for under $200. That sounds a little better than $1000.

[Triathlete]

Mine would stall every once in a while at stop lights on hot days. I would open the gas cap and reclose it and problem would go away. Worth a shot next time it happens.

[mbeach]

Internet copy/paste about your HO2S (heated oxygen sensor) code:
Electrical:
-Water in the harness connector
-Open/shorted HO2S circuit
-Corrosion or poor mating terminals and wiring
-Damaged HO2S
-Damaged PCM
Fuel System:
-Excessive fuel pressure
-Leaking fuel pressure regulator
-Low fuel pressure
Induction System:
-Air leaks after the MAF
-Vacuum Leaks
PCV system:
-Improperly seated engine oil dipstick
EGR System:
-Leaking gasket
-Stuck EGR valve
Base Engine:
-Oil overfill
-Exhaust leaks before or near the HO2S(s)

These pretty much highlight what the other board members have clue'd you in to. Triathelete's loose gas cap causing low fuel pressure, Maugan's bad FPR causing low/high fuel pressure, vacuum leaks etc.
I cut out some of the more odd scenarios (like running out of gas).
Just run down the list and see what's what.

I'm a big fan of using a can of carb cleaner to find intake leaks. I think that'll be the root cause of all of your troubles.

[mbeach]

That PO140 code keeps coming back as a dirty/clogged EGR valve. Search the cleaning procedure here -it takes 10 minutes and uses the same carb cleaner that will help you find your intake leak.

Also, most of the MAF issues that I've found can be fixed by a simple cleaning of the contacts with some electrical contact cleaner and some elbow grease.

[Tone]

I also recommend the 2 combination ODBII gauge units that read and reset codes that let you monitor quite a number of variables live while driving that can alert you to potential issues. Square Scan Gauge that sits on the dash is $125 delivered and the 52mm round unit for pod mount, it $249.00 - email me for more info if questions not answered on the lower left of .info home page.