Oem turbos fail on audi 2013-2017 s6/s7/s8/rs6/rs7 due to oil starvation caused by clogged oem oil strainer. this is a safety issue as the failure happens without warning and as it generally happens while while driving the sudden loss of power could lead to a serious accident. this issue appears to be wide-spread based on discussions available on online forums. audi is aware of these failures and has issued tsb's that identify the turbo oil strainer as the culprit but they have not issued a recall. there have also been various revised versions of this oil strainer over time, each one being less restrictive than the prior. $10k+ repair every 30-50k miles is unreasonable due to fact that oil strainer has been identified to be defective and updated several times by audi.