Ford Repair: exhausts, 4 cylinder cars, london roads

Question
Hiya - I have a ford escort estate 1.8 GTI. It is chipped and produces 140 hp - more than enough for London roads! Thing is - I'm not a boy racer, and the loud exhaust really irritates me. It has a large diameter outflow pipe, and it's stainless steel, so it has both those things going for it, but the loud noise inside the car at 2.5 - 4,000 rpm winds me up. If I have it replaced to a standard model, is there anything I have to watch in order not to impede performance/efficiency? Thanks.

Answer
Brandon-

  First of all, thank you for giving us yanks the term "boy racer".  I've always loved that.  Secondly, please remember that my knowledge of Ford Of Europe is...well...limited.  But I'll take a shot at it.  

  You could probably replace the muffler with a factory (or similar) model without losing much performance.  Yes, you'd lose some, but it likely wouldn't be noticable.  Another option would be to look for a quieter aftermarket muffler and install a resonator somewhere before the muffler.  It won't completely kill the sound, but it will cut down on some of the annoying nature of it.  I'm personally not a huge fan of 4 cylinder cars with exhaust, but with a resonator on there I can usually handle it.  Hope this helps.

Steve