Hi Moozaad,
I had my local dealer fit Duacti Performance end cans and chip to my 1997 ST2 three years ago. It was not cheap at around £500 but I think it was worth it. I chose the alloy cans so they look just like the originals. As a bonus, although they do not carry the E3 marking, neither do they state 'Not For Road Use'.
I cannot vouch for how much the power increase was, but I felt it definitely added to the midrange and top end. Mind you this perception might be due to the wonderful sound that the pipes make. At the right revs, it's enough to set of car alarms!
Make sure you have the emissions re-set to match the chip. Properly set up, the emissions are slightly better than the standard set up. Fuel consumption is slightly worse, but that is due to using more revs to listen to the sound.
Me, winding up the engine and rolling off in the Dartford Tunnel just for the fun of it? You must be mistaken officer!
By the way, if you install the cans without the chip, I am told that the engine runs lean at the top end.
Phil
[Edited on 1-2-2005 by Phil Parratt]