I have a 1999 Nissan Sentra 1.6L. Car runs well

check your vacume lines to make sure they are in the correct position

common fault in this vehicle is air flow meter and temp sensor, if temp sensor fault normally will blow black smoke at the tail pie, air flow meter will have symptoms as you described.

To begin with, if you are revving a cold engine to 6000 RPM, you are asking for a blown engine. Most OBD vehicles are equipped with a rev limiter that will cut off fuel at 3000 to 4000 rpm to prevent you from over-revving your engine and blowing it up. If yours is revving to 6000 RPM cold, then the rev limiter, for some reason is not working while it is cold. I have no explaination for this. The best thing I can tell you is to stop revving your engine so high when it is cold unless you really want to see what an engine looks like after is has gone off like a grenade.

You are right, if the timing chain were bad it would have the problem all the time , not just cold . This to me sounds like a coolant temp sensor . Hooking up a scan tool that can view engine sensor data , i would check the sensor parameters . most noteably the coolant temp an IAT - intake air temp. after sitting over night these should be very close.
Reading Performance Information Data PID Car OBD Diagnostics ECU Chip...

There is a problem with the fuel pump. This is a known problem with the 2006 Sentra and the dealer should have known this. Get your money back

Distributer Signal Output is code p1320........Intake Valve Timing Control Position Sensor Bank1 is code p1140...

Sounds like your throttle is sticking, try looking under the hood for a cable that come out of the firewall. WD40

It is normal for oil pressure to be higher when the oil is cold. As the oil heats up, it will thin out. Since your oil pump is driven faster with the acceleration of the engine, your pressure will also increase. On a engine up to full temp, your oil pressure will probably be around 20 psi and maybe up to 60 at full load. But on a cold engine, you may see 60 psi at idle. I dont know if your high oil pressure is causing your vehicle to stall, but maybe your running the wrong weight/type of oil for your truck. If you live in a extreme cold area, you may want to look into a block heater to help warm up your engine faster.

Check for vaccume leaks and also you PCV valve. check the hose too. Visually inspect every vaccume hose you can find. Sounds like a leak .

remove the front 02sensor and drive the car like that, remove means complety take it apart from exaust, if problem goes away or gets so much better then your catalitic converter at the exaust is restricted and need a new one