Odd over-boost situation? Any BTDT's?

[Taylor]

Greetings all,

After replacing the throttle body switch and multi-function sensor due to 
low boost, I got full boost back (1.4) on my '89 200.  Matter of fact I 
would see 1.4 at best with the throttle body switch, it was a few weeks 
later that led me to switch the multi-function sensor over a A/C 
problem.  From there I would see 1.5 boost.

Anyway, with the A/C on I will see 1.5 bar fast and the car will cut out 
for a brief second leading me to believe I probably have a vacuum leak in 
the Michelin man hose or wastegate hose... however with the A/C off I can 
hit 1.5 and no cut out will take place.  Same problem still or should I 
look elsewhere?  While I'm on the boost subject, another idem pops up at 
highway speeds.  If I apply throttle and the boost shoots up to 1.3 or 1.4, 
it will fluctuate up and down .1, never steady.  Again would this be vacuum 
leak related or something else?

Recent fixes include new injectors, fuel pump, throttle body switch, M-F 
sensor, radiator sensor.... mostly all original parts replaced do to age 
(13 years - 140,000 miles.)

Having a hard time finding a similar problem or BTDT that so hopefully the 
experts here know :)


--
Taylor
'89 Audi 200
'01 Audi A6 2.7T