Power supply control modules

[Potatopete]

i guess this is a question for some of you more techy-minded folks out there.....

My 2002 A4 B6 needs a new power supply control module (sometimes called an under-dash ECU), which has the part number 8EO 907 279.

Audi obviously want about a million quid for this, but I've found them relatively cheap online, used.
My question is this - the majority of the ones I've found have a letter at the end of the part number. Mine doesn't. What difference do all the various different letters make?

I'm sure someone will be able to fill me in on this

 

[Greeny233]

The letter at the end is a "modification" code. So if the part has had an update or modification from original then it'll have a letter. I recently bought a heater control unit and the part numbers were the same except for the 2 letters at the end, 99% of the functions worked but the heated rear window did not. I think the more revisions or updates the less likely it is to work. The best bet would be to ask Audi for the latest part number and go from there.