Would i gain much with putting in a new muffler and header?
 

I found some Bosal ones for about $90 each, would it make noticeable changes?

a ninety dollar header would prolly make it worse lol

my friend had a bosal muffler on his 03 1.8t jetta. He just had a resonator and the muffler the model # was 247211 and it sounded really nice it had a little purr at idle and regular driving, and once you got to the higher rpms it really complimented the turbo sound. When I get another 1.8T A4 the first thing I'm doing is putting that muffler on.