I have the RPI manifold and exhaust system on my '02 +8. The manifolds are welded rather than mandrel bent (which I would have preferred) However welding is perfectly acceptable if done well - which they are.
RPI can supply a less restrictive Cat, but mine is de-catted - it is a smidge on the loud side
I had mine ceramic coated inside and out which I think is well worth doing.
The RPI exhaust seems to have the best reputation for free flow but Librands also have a very good name
