Twizted

4 wires with 6 gauge power wires is called 6/3. It's considered 6/3 with a ground. Having a ground is a nonspoken constant. Yes, the ground is always smaller. It doesn't have to be as big as the power wires and the neutral wire. Especially if you use a neutral wire, the neatral wire takes some of the "left over" electricity back into the breaker box instead of sending to ground and thus wasting it. Going with the outdoor wire (called UF) is definately the way to go. Then you don't have to run it thru conduit, which some inspectors are picky on anyways. Pop N, your wiring is perfect for a 55 amp service and 30 amp outlet and going with a subpanel box for garage/shop is the best way to go. I don't actually own a welder. I have set many customers up with wiring them tho. I went from being a Nissan parts manager to a manager of a fortune 50 home improvement/ hardware store. I'm just saying what is recomended not what can work.Although I seriously doubt that your welder is pulling 145 amps. It may be the rating of the welder but not the amperage draw that it needs to operate. Or your just not using it to it's fullest. Remember 7lbs. of boost is what Nissan recommends but we all know you can get 15lbs. with ease.

Not safely tho. You may be doing that but it is not recommended.

10 gauge wire is only rated for 30 amps. Most generators and all dryers are 30 amps. Stoves are rated for 50 amps and use 6 or 8 gauge wire. 8 gauge will work but 6 gauge is preferred. Anything over 50 feet in length you need to up the wire size. Alot of the newer dryer/stove cords are 4 wires. (Black hot, Red hot, White Neutral, Green/bare ground). If your welder is 3 wire or dryer/stove is 3 wire then you are eliminating the white neutral wire (it's not really needed anyways). Hot tub wiring is a good idea although they do vary in amperage from 30-70 amps so that leaves alittle doubt. Check your specs on your welder and hopefully that info will help. Wiring is not very difficult, just intimidating at first glance.

Certain auto parts stores rent coolant pressure testers. Just leave a deposit which I think is $20. Very simple for anyone to use, just pump it up like a bicycle pump and watch the gauge.

White smoke is the biggest sign of a blown head gasket. On the L-Series engines they seem most vulnerable between 5th and 6th cylinders. Check the sparks plugs and see if they happen to have alittle rust color on them or if your running rich those two plugs will look "clean". A compression tester will work best to diagnosis this. A poor mans way to do it is also to get a pressure test done on the cooling system (the tool can be "borrowed from a local auto parts store or they can even test it for you) the drop in pressure will indicate a leak and if no spray or sound could be found then it's most likely internal. Hence, a blown head gasket. That's wear I'd start. Good luck.

Hehe, Yes they are but worked great for years on all kinds of cars with the Bosch L-jetronic engineering. You can buy new connectors for them at your local parts store. I haven't seen any adaptor that would allow you to "upgrade" to the new style. Not really worth it except for piece of mind and alittle agrovation.

The L6 ones, yes. Not sure about the V6's tho, never needed to check.

Possibility of these two being related is there but not likely. Definately check the shaft play on the turbo and actually taking it off and having it checked would be ideal. Check the vacuum lines and see if your losing any pressure, especially going into the wastegate. Going to 10w60 isn't really a good thing, the oil needs to be slicker/lighter in a turbo car unlike N/A vehicles. Oil sending units also can get clogged especially if the car sat for any length of time. That could cause the symptom you were noticing.

Nissan should have the studs. Most do not carry the replacement for your application however. They were upgraded on the pathfinder and have a star head on them to make it easier, they were also part of a recall and dealerships should still be carrying them. Talk to a knowledgeable technician/service advisor at the dealership.