just had a look at all the above manifolds and i must say while i am no expert (even tho i do make manifolds and exhausts for a living i would say that on all the above manifolds the collectors are crap flow wise, the haywood ones have managed to siamese all 4 ports!!! and on the jamsport ones with the big triangular collectors there could be serious floe issues with the way the pipes enter the collectors as there is a big step up in size just after the primaries that can cause the gases to pulse back towards the engine causing all sorts of back pressure issues. however all thease manifolds should provide better flow characteristics than a standard manifold as the primary sizes on a standard manifold are too big anyway for good flow, i would reccomend 1 3/4 inch on anything up to 200bhp-230bhp and 2 inch an anything above plus there prices are way too high 700quid!!!!! i am looking into making a few differnt designs late this year eg/ standard turbo location and turbo above the box location, the flanges cost me 20 quid and are laser cut in surgical grade stainless which will never rust EVER!! and i cant see any of them taking more than a day or two to develop and i am happy to pass my savings onto other passion ford members probably looking circa 200quid for standard location and 300-350 for above gearbox that is with a new downpipe running down back of engine (efi will be required for this as mfi gets in the way) however i dont want to sound too much like i am slagging the above manifolds off as i am sure they make an improvement over standard as the standard rst manifolds are cack!!!