I have a similar strange wiring issue. My radio plays after the ignition is turned off as well. Only my radio will switch off if you turn off the headlights ???

__________________
James

85 300SD 285k
Charcoal Gray/Grey MB-Tex

79 300CD 142000mi "Rabenshwarz"
Black / Black MB-Tex, Burlwood Int. TOTALLED - 10/24/02 --