Originally Posted by botters

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.