Any idea nhow I can find ....

[AndyP]

... the difference between 600 906 625B and 600 906 625C ?

It's the vacuum control solenoid thing, some background research indicates the A2 version should be the "C" and mine appears to be a "B", although it is very difficult to read.
Mine is labeled in white marker pen with Polo/2003, presumably by a breaker.

 

[spike]

Think the correct p/n for the ATL engine is 6Q0 906 625C, now replaced by 625G

You can do a basic search on this web site - https://audi.7zap.com/en/rdw/
This shows the 625B version was never used on an A2

Sorry I can't find any info on the differences between each unit

Cheers Spike

 

[JIGSAW]

I did some research on that part awhile back as converting to a vnt turbo and found theres only 2 versions that are compatible which are the ones spike has listed above .. hears a link to the page i saved

http://www.darksidedevelopments.co....id-block-for-1-4-1-9-tdi-6q0-906-625-c-g.html

the one youv got is listed for the earlier version and not compatible it seems

 

[AndyP]

I did some research on that part awhile back as converting to a vnt turbo and found theres only 2 versions that are compatible which are the ones spike has listed above .. hears a link to the page i saved

http://www.darksidedevelopments.co....id-block-for-1-4-1-9-tdi-6q0-906-625-c-g.html

the one youv got is listed for the earlier version and not compatible it seems

Thanks that totally supports the conclusion I was arriving at. Hopefully, this will turn out to be an easy fix, as I had expected.