My car is a 85 euro model and the exhaust did have a catalytic converter but I think it was added to meet emission standards when it was imported. I couldn't use any of my stock components besides the piping so I used a chambered muffler up front and a x-crossover style muffler in the rear and it's just a little louder than I would like. I'm assuming a catalytic converter in place of the first muffler should make it a little bit quieter and as for performance I guess I won't now until I do it. I just love the sound of that m110 when I'm going through the gears but when it's to loud long trips aren't pleasant I'm just looking for that in-between area.