200 Turbo Fuel Pump

[TMFINN@ccmail.monsanto.com]

     I have a 1989 200 Turbo, 3-speed Auto, non-quattro.  The fuel pump is
     making burping noises (sometimes it causes the engine to slow because
     it is being deprived of fuel).  I can't tell if the pump is
     dead-headed or cavitating.  I installed a new fuel filter an added a
     can of Techron fuel system cleaner, and it got rid of the problem for
     about 150 miles.  Then it started acting up, frequently.  I added
     another can of Techron and the pump does not act up nearly as
     frequently.  Could this be a dirty fuel tank problem, or just a fuel
     pump that is failing slowly?  I would appreciate any suggestions.  If
     it is the fuel pump any idea where to pick one up cheap, the dealer
     wants about $500?