An Escort RST manifold is good for 350hp, after that the engine 'chokes' somewhat. If you don't want/need/have to spend the money then don't as you'll need a custom exhaust too so you are talking around £900 all in. Personally unless you are going all out (aiming over 350) the money is better spent on the main components i.e. head etc.

However, if I were to have one, I 'would' buy one from Ian Howell (Area 6) and not from Primary Designs (as Nick from PF has one) as we noticed something with it that may become an issue which A6's R&D cured years ago. Just my opinion but I'd spend the money where it's been proven to work not because somewhere else is cheaper or in a magazine!

HTH you m8

Dave