Ralf, it's a RACE car. Expect some dis-comfort. I too run the exact same setup on my Limited Prep G (H now) Wabbit GTI. Header to a flex pipe, to a cherry bomb glass pack, to a 45 degree turn down in front of the axle. I did have a full system, over the axle through a flow master exiting out the stock location, but needed to knock off some weight, so I went with the simplest solution.

I don't wear ear plugs and also think the ringing in my ears and head ache after a session could also be adrenalin.