audi 80 problems

[keith arthur <arthur_k@hornet.lynchburg.edu>]

Hi guys,
I took my Audi 80 to the shop yesterday, and this is what i heard.  My
distributor was lose so he tightened that up, and that made it
better,but the enine still cuts back at around 4500rpms.  Tomorrow he is
going to check the fuel filter.  He also said he thinks it might be the
ignition coil.  He said as the rpms increase the voltage from the
ignition coil decreases.  So that might need to be replaced.  Where is
the best place to buy a ignition coil(if thats the problem) from, and
how much should i expect to spend? 
thanks
keith