Tungsten

This is what the oxygen sensor looks like stuck into the mid pipe. If yours is missing or damaged you will have issues. Also, unplugging the sensor and running the default map might be worse with a high flow exhaust than factory. Definitely check the sensor out.

Those fog lights are actually pretty good if you use them for fog.

What kind of an exhaust system are you running with those headers? If you are using the factory piping you are actually shouldering off the flow of the exhaust and there is even less exhaust going through than before. The short tube 90-95 headers call for a 2.5" exhaust system for the best performance. I ran a factory sized system with the headers at first so that I could just get it back on the road and noticed no difference. Then I finally had the funding and a chance to develop and construct a full 2.5" exhaust system and noticed a big improvement. If I was going to do it again I would just build a 2.5" mid pipe with the appropriate O2 sensor bung and then get a 2.5" Gibson cat back.

I would go the VG34E way instead of getting a VQ35DE. You get an iron block instead of aluminium and only one set of cams to worry about instead of two. Efficiency wise I expect the VG34E to perform better because in theory it should have more low end torque than a VQ35DE. The older VQ powered Pathfinders manage to only eek out an average 14 mpg. With that said, getting a different truck is definitely not a bad idea if you have limited time and resources. That really depends on how good you want it and how much time you can spend on it.

As far as the ECU goes... If you have an early Pathfinder with an OBD 1 you can pretty much extract the old ECU and put whatever else you want if you are unhappy with the stock tune and it will be street legal. With OBD 2 you can do the same but you may have trouble passing inspection because they have to connect their own computer to the port.

FYI: Running more than 4 lights at a time can get you into trouble in some states. Keep 2 of them covered up or don't run the fog lights with the driving lights.

The problem with that is they cost significantly more than standard bulbs. Using OEM bulbs with properly cleaned and aimed headlights should be just fine because they have to be made to specification. If you can afford it, go with the XtremeWhite PIAA bulbs (not the blue tint ones).

Of course finally found what I was looking for... Nissan did make H4 bulb "sad eye" style head lights after all. This is what happens when I put in Terrano head lights: These are the answer to crappy DOT headlights.

E will be way too stiff even with extra weight. D is already bad. I currently run C rated tires and they are already on the firm point. I would not go over load range C even with extra gear on board.

Bingo! Heads up to nunya for suggesting the members rides section... Just found one belonging to kiwipete. They are in fact E code housings. Judging from the pattern, they are made for RHD, which would make sense because kiwipete's truck is RHD. This logic would dictate that LHD housings exist as well. The LHD ones should be similar but with the pattern on the lens mirrored the other way. So in fact Nissan should have had 3 different sets of "sad eye" halogen housings: DOT spec, E code RHD, and E code LHD.

You can get around the wiring issue by installing water proof connectors.

You can get brighter bulbs but they do not last as long. Stick with OEM replacement bulbs. PIAA bulbs are great but they only last about 4 years before one burns out. If you are having problems seeing at night, you should try removing yellowing from the plastic lens with a kit first. Do not use a HID bulb without changing the housings. HIDs require different housings to aim and focus the light. They need fish eye projector lenses. Reflectors can work too but they have to be special made for HIDs. Running HID bulbs in halogen housings will throw the beam pattern way off and you will be blinding people and possibly lose your high beam.

Very nice. There is really no way to tell them apart unless you look really close at the frost pattern meaning directly into the headlight. The US units should have a DOT beam pattern so they are frosted in a way to produce that kind of a pattern. Here is mine for comparison:

I'm trying to find out if Nissan ever had E code "sad eye" headlights. Can anyone with a Terrano take a picture of the headlight lens? I want to find out if the Pathfinder DOT pattern housings are exclusive to the US.

More traditional? It's just one step away from being coil on plug. They only put that distributor there to get away with only using one coil.

Can you apply a manual vacuum to the valve and see if it holds? The engine should struggle if the EGR valve is open when it shouldn't be. That means the valve is not the problem but there could be a vacuum leak instead.

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.