New to this forum, my daughter recently purchased a 2016 A8L 3.0T, took it to the dealer due to a P0430 emissions code. Service tech said it is a faulty cat, to be replaced under extended emissions warranty. Also, he said the vehicle showed another code for a faulty pressure regulating valve (he did not tell me the code), cost of repair, $2800. This fault code did not show on my daughter's recent trip to Autozone, only the P0430. So what is the Pressure Regulating Valve and what is the likely cost of repair at a non Audi repair facility? TIA.