Inputs solicited -- 1990 - 90 - 20V Quattro

[superba]

Hi All,

I discovered a 1990 Model 90, 20V Quattro for sale at a reasonable price.
It has about 130K miles on the odometer.  Other than the more obvious
questions, are there any hidden gotchas that owners have discovered, or
previous owners?  Am I compounding maintenance problems by adding a quattro
drive train?  Ditto for 20 valves vs 10?  Is there an absolute bingo number
for timing belt change;  the 7A is an interference engine?

TIA.

Cheers!

Jim Jordan