Just for the sake of experimenting I've been playing with the idea of installing an RTEK 1.5 modified US-spec ECU in my T2.

I put in a stock N333 ECU in the place of the original N344 from my car and it seemed to run fine, no starting issues or weird failure signals, so it seems they are pretty well interchangeable. I think the only differences might be in some subtle bits of code or limits.

I had one of the guys in the electronic countermeasures maintenance shop at work do the required soldering for the RTEK chip, a case of beer well-spent in my humble opinion. I then installed the RTEK ECU in my car and carefully ran it for a while and it seems to work quite well. Now all I need is to get a bunch of 720cc injectors and go for a RTEK 1.8 setup...

 

Few months ago, i PMed hIGGI, asking him about this matter, and he told that he is using US spec ECUs with Rtek with no issues. I certainly will buy an Rtek 2.1 as soon as possible... and i´m thinking about 720cc RC injectors to use with it.
Good luck with your setup and let us know if you got success.

 

Soon as I get the coolant seal leak in my engine fixed I'll go and do a proper test on it. But that will have to wait for at least a month due to me being in the US for my job.

 

Yes, we have few EU spec S4 TII cars here running Rtek 2.0 and 2.1

And yes, harness and all is stock (EU) and just ECU is US spec (n333 or n332) which we just purchase thru our friends in US, have it Rtek-ed there and then have it shipped to Europe.
Used ECUs could be had for ~$50 and its most likely cheaper than having your EU spec ECU shipped to US for modification.