Ignition Timing

[achoeypatkul@hqfaus01.unicef.org (Amnat Choeypatkul)]

     Hi Audi pundits,
     
     Could any one pls shed me some lights.  (I have an '89-90, 
     2,300cc-5L/NG 10V engine, w/ 68K miles.)
     
     About a month ago, I brought it to the Audi Service Center to get 
     60K-services--which I paid about $1,300 to have a moron dumped 6 qt of 
     oil into my 2,300cc engine (Audi has recommended 3.7 qt w/ the filter 
     replaced).  (Well...I really felt as it was 60K ripped-off.)  :(
     
     Since I got my car back, I feel the engine does not have power as it 
     was.  The engine, sometimes, keeps knocking and has no power at all.  
     Of course, I'm using the expensive Super/Premium/Whatever-you-call gas 
     (from Mobil/Exxon/Shell/Amoco) w/ 93-Octane at least.
     
     According to the service records on my bill, here what it's read:
     1) Check Ignition Timing (+16 degrees)
     2) Engine Vacuum (17 psi)
     3) Fuel Pressure (90 psi)
     4) DPR MA (0 MA)
     5) All engine setting to factory specs
     
     Here are my questions...
     1) Is the above "Ignition Timing" (+16 degree BTDC) correct ?
     2) If not, what is the standard/recommended for the "Ignition Timing" 
     for '89-90?
     3) Also, pls let me know where/how do I start to fix this "lack of 
     power" and "knocking" problems.
     
     MTIA,
     Nat
     
     '89-90 (68K miles)
     Note:  I don't have Bentley services manual yet, since I spent most my 
     $$$ for this 60K ripped-off.  snip..snip..!