Tungsten

The EGR valve does not work until the kill switch turns off. That's done to avoid having the EGR interfere with engine warm up. A stuck EGR in the open position will make the truck sluggish and unresponsive. A closed one will not do much on a VG engine. The oxygen sensor, coolant temp sensor, and EGR will have an effect on NO emissions but it will not have as much effect as a catalytic converter that's going bad. From those numbers it is definitely looking like a catalytic converter.

Typically the ECU throws that kind of a code when the expected resistance of the coil is different from what the ECU expects. Maybe one of the connectors going to the coils are dirty or foul?

Welded diffs on independent suspensions are extremely hard on bushings and suspension components. If you are doing this on an R50, definitely get locking hubs so that you can unlock the diff for on-road use. A locker is definitely better than a ghetto rigged welding solution.

Run some carbon cleaner through the system. That should help with power too. If that doesn't help, high NO emissions means there is an issue with the catalytic converters.

What has been said above. For auto, there is an inhibitor switch to prevent the vehicle from starting when it's in gears other than P or N. Either the switch is bad or the shifting linkage may need some adjustment. There is a switch like that for manuals too but it has to do with the clutch function to prevent starting in gear.

Throttle body spacers are useless but plenum spacers might make a difference.

If you want to do a little project how about installing some lighted visors and a map light.

Not necessarily, the P codes are generated by the OBD tool and not by the diagnostic computer.

Those are oxygen sensor codes.

I'm wondering about the oil pan seal and the drain plug. The oil pan gasket can leak sometimes and a free fix is to torque the bolts.

Good call on the wires. An exhaust leak will cause bogging because the oxygen sensor will pick up an incorrect reading.

Just one advice. If you are going to use polyurethane bushings they will give you a much harsher but stiffer ride. Also they wear faster. I have tried both rubber and poly bushings. The rubber ones last longer and have a better ride. The poly ones don't last as long but are stiffer if you want that. I have mixed opinions on using poly vs rubber on the strut rod bushings. You want them stiff but at the same time you want them to last long and not throw the alignment off. I currently run aftermarket rubber ones there and they seem to be fine. Just use factory sleeves because they fit over the strut rod better.

I made the map light come on with the dome light instead of the luggage light. Just a personal preference. You can just add a ground wire from the dome light to the luggage light if you want the luggage light to come on with the dome light.

There is one big difference between the two. The automatic has a different variable length intake manifold with power valves while the manual has a regular intake manifold.

The most accurate reading for the coolant temperature is acquired from the upper coolant neck on the return line. This is where you have 2 of the temperature sensors. One for the ECU and one for the dash cluster. I have used the dash cluster sensor for my fan controller when I did the E-fan swap.

You can switch to a carb and there's even a member here (Mr.510) that sells adapters to attach Holley carbs. It would make everything simpler but the fuel economy might go down a little. Mine used to bog like that when I had a bad oxygen sensor. Try disconnecting that and see what happens. Make sure you also don't have an exhaust leak.

I don't know how they are like on the R50 but the fog lights on antique Pathfinders are real fog lights. They have the correct bulb and pattern. Some people swap out the fog lights for driving lights or install driving lights if the fog lights are not there. I personally don't like that because it gives the illusion of safety and does not make you really focus on what is up ahead. People do this mod because the factory sad eye headlights are almost inadequate for use at night. Using the lower fog lights on the R50 as DRL is not a bad idea but DRL lights don't need to be bright in the first place. On WD21s the factory DRLs for places that require them are high beams that are run at half the brightness (or about 32.5 watts). Also running fog lights without running the headlights is actually illegal in some states which is why Nissan makes the fog lights turn on with low beams from factory. You want to check with your local laws on that.

I'm not even sure the factory pre-historic ECU is going to be able to cope with a modern DOHC system. A donor truck with the engine would be the way to go.

Unplug the sensor then so that it does not pick up the leak. It's not the best solution but should be good until you fix the source of the leak.

The VQ and VG are actually directly interchangeable. You might run into some fun with wiring for the computer though.

Sounds like a MAF sensor issue to me. Could be that or the oxygen sensor. Do you get a code?

Alright if you're happy with it I guess it's good. Remember the job of fog lights is to light up the corners of the road, it is not to compliment the headlights. Even basic filament bulbs work just fine. HIDs are not a good idea for fog lights because they are not ideal for bad weather driving at all.

This is why you don't shop at Walmart with a truck like that.

There might be a special way you have to cure it in order for it to be actually flame proof. I haven't used VHT Flameproof but I have used other VHT high temp paints and they work great. I painted my bumpers with matte VHT roll bar paint and it looks great just like original.