This is a common problem with the aftermarket intake manifolds,
i'm assuming its fouling/touching where the bolts go for the manifold/extractors?
if its a redline, and never been on a car before, there is a lot of cutting, machining to be done,
have you checked the manifold face thickness (where it bolts to the head) as opposed to your extractor face thickness?
you should be able to get away with the manifold you already have, sounds like you just need to persist with the manifold to get it right,
if possible it would be great if you could post up some pics so we can all get a better idea on what's going on,
cheers phatke30!