Up for sale is this good used Auto Ignition coil & module assembly.  Unit was removed from a 1990 90, 20 valve, and will fit a variety of other Audis. 

The part # on this unit is 443905105C  - These generally last around 150,000 before a failure, but when it does fail it will prevent the car from starting. If you have spark from the coil but not at the spark plugs, this is often times your problem. The ignition module portion of this unit is the device that "hears" the hall sensor in the distributor, fires the spark plugs and tells the ECU, "we are good to go, turn on the fuel pump and start working!" Generally if there is a problem with the ignition system on Audi / VW's it's either this unit or the wiring to the hall or crank sensor that goes bad. These are fairly easy to replace, and they are over $590 from the dealer for an OEM unit. This will fit many different Audis, and others. 4000, 5000, 90's 200's possibly some Vanagons, Jettas, Golfs, Scirocco, Passat, possibly more models, your best bet is to match the part number with the one you are replacing. The OEM manufacturer on these for Audis is Hitachi,

Get the part you need here for cheap! Thanks for looking! This comes with a 30 day warranty. If the part you receive goes defective in 30 days time, just return it and I will either refund or replace.