umm, dude, ask kevin! I got 50 ft of 5/32 hose for like, $15 off ebay! 5/32 is what is used for most of the car, as Kevin said!
Hey look at that, for once I'm the one giving advice!
http://cgi.ebay.com/ebaymotors/WINDS...mZ300189790333
or buy this one and you're set for whatever car!
http://cgi.ebay.com/ebaymotors/VACUU...mZ190228878504
EDIT: but then, I got an S5 N/A so there might be a few hoses that are different!