I had the cat back first and thought it was deeper than the original but at cruising speed it was about the same, it was only under full acceleration the difference was apparent. Now Iv'e had the DP and cat the difference is 
....Same here. I had the ordinary Milltek Catback for a short while.
The quieter Resonated version is still louder than stock but not by much. The louder Non-Resonated is only louder when the engine is under more revs.
Milltek don't fit their systems to customers cars at Derby unless it's sometimes a replacement or you are testing for them. They need their workshop and time for their own development cars.
