I can't speak for the floorboards.
But, for the other points.
Reliability largely depends on you. If you're not the type to get your hands dirty, and go the extra mile to care for your car, like a parent loving a young child, they can be costly. Most of the problems people have in these cars are electrical things, and the transmission. The motor (the 4.2) is by and large one of the best motors Audi has ever made.
The weak point on the car is the transmission. So, for best reliability, every 50k or so, I'd drop the pan, and change the ATF if it's in good condition. If it's in bad condition (metal, burnt, etc), I'd flush it and run the best ATF you can through it to squeeze life out of the thing.
Hmm.. So yea, my car has 288k on it, it's on its second transmission, and the motor uses oil, but I bought the car with the intention of replacing both.
You might comment to where you're from. If you're in GA (GA cook), then your car may have been a flood car, and the carpet was removed due to mold.
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