Help: 200 20V cut-out

[Ferry Stolp]

List,

I need the help of you guys.
A good friend just bought an '89 200 tq 20V, euro-model with the
RR-engine (yup, it made me drool!).

Car stalls at random rpm's, mostly about 4000. It will restart right away
perfectly and runs very smoothly.
He read the codes but they where all clean, no faults.
The car was resting for about a year but fired right away after installing a
fresh battery. He also did an oil change.

My first thought was the famous-UrQ-temp.sensor but I doubt this is
causing the problem because the engine completely stalls and doesn't just
hold back at 4000rpm like the UrQ. Or am I mistaken?

Any thoughts? Things to look for?

Second (minor) thing: how to get the radio (Audi Delta) off  'SAFe'??
I know it's a combination of buttons to press to enter the code (which he
has)
but we stopped trying after 30 mins :)
Any BTDT's somebody??

TIA!!

Ferry Stolp
The Netherlands
www.audicoupe.nl