Thanks for the great replies I'm getting, very inspiring.

I do believe that there is a lot to be learnt from simply comparing tunes and looking at other people's work. I am actually really inspired to start learning properly now.

So I've decided (with everybody's help) that the proper way to go about this is to get a spare ECU and create a clone of my current one. Then I can flash to my hearts content with no real fear of it all going wrong.

I'm going to build up a cable harness for bench testing over the next week or so, so hopefully getting a functioning "workspace" should be simple enough.

With that in mind... Does anybody by any chance happen to have a spare ME7 1.8T BJX ECU lying around anywhere? I will pay good money for it. I will get the serial number tomorrow when it's light!

Also... Immo off... Just out of curiosity, how does that work? I assume it is just coded out of the EEPROM? Might be worthwhile for me if I am going to create a debugging ECU. Anybody have any documents or links about it that I can read up on?