To use the adapter plug that hooks up to an Audi Alpine...
a) There's gotta be a mode button on the radio face ( hard coded Gamma only )
b) the harness needs to be there ( late '92 A100 & newer ) Up till '96 model
year
the Audi CD player was only intended as a port installation.
Your best bet might be CD player with an RF adapter from a monetary point of
view.
Vince Lyons