What are the differences between the two?
I've found info on Passats for this year, and S4s, but wasn't sure about the A4s.

 

pretty sure they didnt have a 01.5 A4

 

That answers that question. Thank you!

 

Considering some retailers sell things specifically for the 01.5 and the 2001 model - and also because the ecu's differ (ch vs m).. I'm pretty sure there are 2001.5 a4's. As to what the differences are, I'm not sure. I do know, for the timing belts there are differences with one using a pin and the other using a bolt.. which is why vendors ask if you have an early or late 2001 a4 when buying a timing belt kit.

I could be wrong, but a few things are leading me to think there definitely is a 2001.5 a4 and the differences are very minor.

 

There is a 2001.5 A4 :] i have one. The vin pull up at the dealer confirms it. just thought i'd post to share :P