AVNTGRD

it’s in the shop. on the list of things:

- steering rack leak - leaks dry in a matter of minutes
- tie rod ends
- all four upper control arms
- headlight sensor
- left and right inner and outer CV boots
- coolant temp sensor
- upper radiator hose
- cruise control/signal stalk
- rear brake pads
- there's more to be done in the future that isn't on this estimate

$6000

it’s my local awesome indie audi-VW specialist shop.

if i even keep the car, what are the parts for which aftermarket upgrades exist?

on the pro side of things, i only paid $3500 for the car.

2002 S4a manual 180k miles - one of the last b5 S4 cars off of assembly line.

gk1

Fun build you got there.
The steering rack is a bummer and I assume the most expensive part.
The regular S4 solid tie rod ends are already an upgrade from the A4 rubber bushed ones so not much to upgrade there.
I hate to add to the pain but if you are going to do the upper control arms I would also do the lower ones since you are at 13 years and 180k miles and are going to already have everything apart.
I would also suggest getting rebuilt axles/cv joints instead of just replacing the boots. Check out raxles.com
I would also replace wheel bearings too. Same thing...everything is already apart...removing reinstalling the wheel bearing really isn't difficult for a pro at that point.
I only mention these extra things because they are all things that went on my old B5 at maybe 50k miles...unless you know if they were already done previously.