ECU Part Number 028 906 021 xx Identification

hello,
I am searching (apparently quite helplessly ) for information about my engine control unit.
Engine is from a Golf 3, model 1Z (engine control unit), manufactured in 8.94.
The engine is now installed in a T3, and it appears that a different engine control unit (likely a WFS unit) was installed during the conversion.
Original license plate number is.
(Bosch 0 281 001 316/317) 028 906 021 AP
has been changed (handwritten) to 028 906 021 G.
On my chips, it says:
A73 BA100 0E00
and B73 BA100 E700
The chips have been socketed after the fact and hand-written, but they definitely don't offer any more performance (an AAZ engine with LLK is just as fast...).

Is there a list of device numbers/mappings available online?
The 028 is for the TDI engine, while the 021 seems to be used in the Golf (but also possibly in the Vento?).
Specifically, the ending characters are the big question! For example, would a part number like 028 906 021 FB fit my 1Z?
What would happen if I were to insert a chip with a different identifier?

Where can I find information about this? (I've spent a few hours searching the internet and then browsing this forum, but "AP" and "G" seem to be unknown terms.)
Thank you for the information!
Hi, Marcus.

PS.
at least now there's half a liter less oil in the pressure sensor,

'I used the 028 906 021 FB (from a Vento) in my 1Z engine in a Passat, and it works! The only thing I had to do was slightly modify the connector.'

The ECUs with a single letter were the 'first generation' (8-bit???) and were later replaced by the ones with two letters (16-bit???). Based on my experience, the older ECUs cause problems with VAG-COM, while the newer ones work perfectly fine with it.