Remus exhaust, does this require a bike retune?

[stevefire]

I have recently bought a Fazer 600 s 2004 model, great bike. It came fitted a Remus exhaust, however when riding at low revs i have noticed a "spluttering" "jerking" feeling in the throttle. I still have the original and am massively considering putting it back on as 1- its loud as F*@k and 2- its becoming an irritant when trying to accelerate and just getting a "choking" feeling from the bike.
Has anybody fitted one of these before? did you have the bike retuned after?
Thanks to any help.