Unfortunatley until someone buys one and has there car dyo'd before then after its hard to say how much horsepower / torque its going to make and at what part in the rev range.
Dont for get to take into account that if you bought that manifold you would either have to adapt your std cat to fit for the MOT which unless you are doing it yourself will cost you more money.
Also if the quality is sub standard it could cost you more in labour to fit the manifold.
A pulley and an exhaust manifold should be your first mods if you're looking for horsepower.
WELCOME TO 1320autos.com 
