bugs

[Mark Zvolanek <mzvolane@sydney.ipex.com.au>]

Would anyone be able to help with one of few bugs in my 91 Audi 90.
These are in order of importance.
1. During driving, I switch on the head lights and the power to the radio   
interrupts for split of a second.
2. As the car engine warms up, revs decrease to below 800, resulting in   
rough idle.
3. Slight high pitch sound coming from boot section of the car. Maybe   
fuel pump? Could it be the pump,  even if it has been replaced two years   
ago by previous owner.
4. How often should the injectors be cleaned
5. How do I remove/replace the light globe behind the digital clock   
inside speedo indicator.
6. How do I remove/replace the light globe in fog light push button.

Please anyone help!
Any suggestions would be appreciated.
MarkZ