Milltek ValveSonic on S5 Sportback

[Drew S5]

Looking for advice!

I have spent a huge amount of money on a Milltek ValveSonic exhaust because I wanted to run the car quietly when using it for business and open the values when having fun. The problem I have is that the system is very boomy and causes lots of drone especially on the motorway under load even in quiet mode. Milltek say this is a fitting error as it shouldn’t do this but the installers say there is no problem with the fitting and neither side want to accept blame or help me any further. 

 

Please help!