Good question, why did you remove it??
All smoke and no poke with these, plus mine gets me holla'd at as people think your going twice as fast with all the noise!
Did you feel as if it had any more power though? I do like a bit of noise hehehe I mean it helps if you have a decent sized engine and brand in the first place like a 2litre 16v GTi instead of a 1.2 Clio or Vauxhall Corse *shudders*
Mines only the 8v, to be hoenst, it doesnt feel any more powerful, but say you stick in 2nd and floor it too 60, over 3000 rpm it soudns awesome, then change to 3rd and do the same to 80/90/100 it sounds awesome. But then again, i drive like a nob.
But as for performance, really is no difference, few bhp extra maybe, but not noticable.