I own a nissan safari canrod 4.2 non turbo deisel lwb .I have owned for nine years. I have regualy serviced it my self :eg,replaced 2 oil filters,new 13 liters oil, blew out air filter; and this time also changed fuel filter.My question to you is; Without fitting a turbo.how can i better its performance.It always feels like its draging a dead cow behind it every where.Dont get me wrong ,the motor run perfectly ;just doesnt feel like a 4.2 ???

Always replace the oil pump or at least, re shim it.

5W30 maybe synthetic your choice, filter Fram XG9688 or equivalent , 5.81 US quarts of oil.
link below may help, press the helpful button
Oil Filter Change Hyundai Sonata 2011 SE 2 0T Turbo

black smoke is not enough air or excessive fuel
if turbo , the turbo is not working and boosting, injector failure
incorrect fuel in system ( petrol instead of diesel)
water in fuel will damage injector tips

A stock 2000 Maxima engine is non-turbo and 5W30 oil is recommended by nissan. As the mileage on the engine increases, you should switch to a heavier weight oil, like 10W40.

Th only thing you can do is have it inspected and have an oil service. Anything else will require a more indepth teardowm and diagnoses. Its possible the last oil service they put the wrong weight oil in it.

unfortunatly nisan only nuilt the deisel trucks for a few years so any engines youll find will be the same as what you have

No different from any other oil change, just reset the oil life on the dash if it has one which i believe it does. The oil grade is 5W-30 on the turbo engines and 10W-30 on the non turbo engines. If you like you can go with the synthetic oil which will give you up to 25,000 miles or 1 year before service, but you do have to replace the oil filter every 5,000 to 7,000 mile and top off the synthetic oil which in the long run be cheaper then changing the oil and filter every 5,000 miles or six months for turbo and 3,000 to 4 months for non turbo engines. Good luck and hope this helps. 

Distributor is at fault

look for the turbo under the hood it looks like a snail kinda

My sincere apologies for the extremely delayed response.
I am personally going back to answer your unanswered questions.
I have only been a free contributor to this site for the past 4-months.

I do not know if you still need this information, but I am going ahead and answering it anyway.

1. Non Turbo =VG30E. Turbo = VG30ET. In any case the Engine Cylinder numbers, Firing Order, and Distributor Connections are the same.

For the 3.0L:
Firing Order:
1-2-3-4-5-6
Cylinders:
(back of engine)
5--------6
3--------4
1--------2
(front of engine)
Distributor:
....(back)
.6......5......4
.|.......|........|
V......V......V
|..................|
|..................|
^.......^.......^
.|........|........|
1.......2.......3
....(front)

2. I am not sure what what "cam adjustments" you were looking for. I am sure you probably have taken care of that or found what you were looking for. However, in most cases the person is really asking about the Timing issue.

Click on the following Link for the Timing Belt/Chain Diagrams.

Again, my sincerest apologies:
http://www.2carpros.com/car_repair_information/year/1988/make/nissan/model/300zx/1988_nissan_300zx_timing_belt_diagram_marks.htm