Carlos - I can tell you early next week when Ive got my Willy back. It had a de-cat pipe on when it went in, but its having a new cat fitted. If it feels sh*te, Im putting the de-cat pipe back on.
It felt pretty good with the de-cat on, but it made an annoying buzzing noise at about 3000 - 4000 rpm which was very audible from outside the car and Im not keen to have it back.
Seen a couple of posts this week saying that it doesnt make much difference, so we shall see....Ill let you know how it goes.
Rhys