Who makes a stainless steel 3 bolt flange that fits on an S5 turbo and connects to the downpipe....for cheap? Will any 3 bolt 2.5" flange work?

 

try the flanges section of atpturbo.com . right now the site is running slow for me though.

 

not necessarily. even though the pipe is the same size, it doesn't mean that the flange will be. most people will offer flange dimensions before you order if you ask. or, you could just order one and have a custom flange put on it.