is this definite, tested etc as got some decats but won't bother if they eat torque!
on there own they might be alright, but i've seen it on plenty of other cars where the exhaust system is made "free flowing" yes the BHP gain is very good, but its all at the top end, and in order to make any use of it you'd need to be 4th gear doing over 120 mph or more to see its advantage.
what you tend to find on most fully free flowing systems is they lose a load of grunt low down, like pulling away at a jun ction/lights etc most don't notice it with the added noise etc makes them feel like they are faster.
most people only care about the numbers they can claim down the pub, but real world driving and the fact that on road cars they won't pass an mot and you need standard equipment on i wouldn't bother with them unless you were building a track car.
i also don't like them on the zed because they tend to lead to a horrible raspy noise. to me it sounds chavvy and cheap, but to others they think it sounds "racey".
but this is my personal opinion, and many disagree with me, so your best bet would be to g oand try someone elses car who has them already fitted. if you like them fit them, if you don't, sell them.