Engine codes P0340

I have a ''nice'' problem on my Nissan Sentra 2005 SE 1.8L

Since I have the car (back in 2008) I have P0340 codes always comming back.
I've been to ALOT of Mechanics and two times to the Dealer.
They replaced the following:
Catalytic converter,
Timing Chain,
Crank Sensor,
Cam Sensor,
Coolant Sensor,
Mass Air Flow,
Throttle Body,
Fuel Pump Regulator (Recall)

I've cheked the oscilloscope for the cam and the crank, every signal is conform to the specs.
There is no vacuum leaks.
I've cleaned the injectors.
The fuel pressure is perfectly fine, always good with the specs.

THE ONLY THING which seems to make it better is if I plug the car for about 30 mins, the problem is not there.

Please note that I am from Quebec, Canada, and its currently about -20 celcius outside.

I can add that I just looked under the valve cover if everything was alright, everything is ok.

I can add to the symptoms that when its hot, the idle is stuttering a pretty damn high.

I tried to use a injector cleaner tank at the normal regulated pressure to eliminate the possibility of the fuel pump, same trouble.

So its definately not the fuel pump.

I Bypassed the whole harness to my Cam sensor, still doing the same trouble.

I am about to replace the ECU, im out of ideas.

Is there any way to reprogram the ECU myself? I know I only need to put the car serial into it so it can handshake the other modules. But I only have the old MasterTech and a Genysis by OTC. It would cost me about 220$ to have that serial swapped and im not sure if it will work for my problem.

Maybe I could buy a OBDII connector with a smart cable so I can reprogram my ECU on a pc based application?

Thanks alot I hope you can help me

Tony.

Thanks for the advice, I got a rebuilt unit from ebay and plugged it in so far so good, no codes. I will drive it and get back to you if the light comes back on. Thanks for your help. I love this site.