Tank Assembly problems of the 1999 Audi Quattro

The abs control module has malfunctioned and the cost to repair is over $1600. I have been to both an Audi dealer and received the $1600 quote, and to my personal mechanic who said the part is quite easy to replace but expensive to purchase. I have read hundreds of comments from other Audi owners who have experienced this problem. There has been shown a 90% failure rate for this part in Audi's. The car also has an issue with the gas tank where it does not release air from the tank properly and causes too much pressure.