Pop in radio when A/C cycles

["Mike Miller (Volt) (Exchange)" <a-mikemi@Exchange.MICROSOFT.com>]

Being fairly new to this list, I hope this has not been covered too many
times before. Couldn't find anything in the archives.
I recently purchased a 91 200Q - 73k mi and looks like new. There is a
loud pop in the radio when the A/C cycles. I know that Audi has a kit
for ~$120US to fix this. Looks to me like the kit just puts a xener
diode across the leads and replaces the relay. 
Has anyone had any success fixing this any other way? Like maybe just
putting a large capacitor between the power and ground? Could do this
for under $5.
Also curious how much boost I should be seeing. Varies between .2 and
1.4. The car recently had a vacuum leak repaired that limited the boost
to 1.3 and also greatly flattened the boost curve. Any "easy" ways to
gain additional boost?
Anyone need any parts off an '81 4k 5+5? I have one for sale and one
that I am parting. One annoying bug on the 4k - intermittently the
alternator quits charging. The belt is new and tight. Has done this on 3
different alternators. Revving the motor to near redline or hitting a
series of bumps (like lane dividers) will bring it back to charging
again. I have searched for a loose wire, but have not found anything.
Anyone have any ideas?

Mike Miller
Bonney Lake, WA
81 4k 5+5 (2)
91 200Q (Pearl)