Titus you might want to speak to an exhaust specialist. Many exhausts can be bought with or without a "resonator" which is meant to take the drone out of the sound.
In yoooffff tuning circles they will often delete these to make the Honda/Nissan 1.3 sound like a rorty1.31 monster that they think it is.
When I had my GTR33 many years ago I deliberatly got a dual pipe system with resonators to remove the motorway drone and also raise the note from the single large pipes which were deep and loud as a result.
