I just bought a 1997 A6 2.8 Quattro cause the price was unbeatable. It has 160K miles and I bought it for $2250. Maintenance records for it are very scarce, with only a couple oil changes recorded. What maintenance service should I have done to it? Would you suggest synthetic or conventional oil? Is it possible for me to do the a4 software conversion? Thanks.

 

I think you are in line for the second go around of timing belt, idler, tensioner, waterpump, thermostat. Use a good oil filter, mann or wix and synthetic oil 5w-40, have the tranny serviced use synth fluid. replace break fluid, fuel filter, plugs/wires, air filter
clean the TB. Some of this may be overkill, but at least you will know what has been done. Also, when replacing the break fluid I got stainless steel break lines for the front and it makes a big difference in the stopping power. Paragon Performance in California has complete kits. You may also want to check your vacume lines for cracks, dry rot.

 

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The 1997 A6 Quattro has a problem with the front driveshaft seal at the center differential leaking. This would not be a problem if it were easy to refill, however the fill hole is above the CV joint heat shield and the cataylitic converters. The exhaust pipe bolts and the exhaust manifold studs usually are so corroded by 160K miles, that they may snap off.
You will need for the USA and Canada the BentleyPublishers.com Audi shop manual CD. You will want to replace this leaking seal, because you don't want a burnt out dry center differential.
You may want to replace the 8mm steel exhaust hardware with 5/16 inch stainless steel. You can get 8mm x 1.25 and 5/16-18 dies, to make your own stainless steel bolts and studs.
The right exhaust manifold can be easily removed from the 2.8L AFC engine, however the left exhaust manifold has a coolant pipe in the way.