Basically (people quote me if im wrong) tubular manifolds are needed for over 600bhp, most would use a 2wd item modified up to that bhp, also i think you may be using the wrong turbo for your power output possibly a gt30 would be best around your power figures and not the gt35, unless you are aiming for more power in the future?

The only reason im selling this one is ive bought a primary designs item, which is costing alot more, this is a cheap very good manifold.

There may also be plus sides to running this manifold but its beyond my explaining so will leave upto the experts to jump in.