2.7T heads - difference between A6/S4/Allroad and RS4

[vtraudt]

I have a set of supposedly RS4 heads.
How can I tell if they ARE RS4 heads (or RS4 cams)?
What is the difference between 'normal' 2.7T and RS4 heads (cams)?

[4rings2turbos]

There is a stamp on the heads, and RS 4 head will be stamped AZR or ASJ. The stamp is located on the front inner corner of the bank 1 head and is visible looking down at the engine from the top.

There are many differences but I have to imagine there's a nice description of the differences out there.