I'm sure this topic has been beaten to death over the years but all the threads I find are quite old and have links to vendors that no longer offer DPs.

Does anyone know who still offers DP for the C5 RS6?

Best I have found are these cheap ebay ones(unsure on fittment):
https://www.ebay.com/itm/Audi-S4-4-2L-V8-RS6-4-2L-DOWNPIPES-WITH-CAT-Ko4-028-Ko4-029-Audi-Upgrade/123525995704?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.

Contacted a few places that used to sell milltek DPs but no longer do. I'm sure they would be more than I would want to spend anyways.

Thank for the help!