I spoken with Neal about these, and the subject of matched exhaust port has been covered in another (250) thread.

As Neal says you need to modify the header of the pipe as the NSR150 cylinders have a different angle port mounting face than the 250, which is why our manifolds for the 300 kit are angled.

I admit that our manifolds are certainly not ideal, but in the interests of using the same pipes we will continue to supply as is.

The straight manifold alone with gain power as experimentation has shown that angle changes can disrupt exhaust flow, especially close to the port where the gas is still expanding somewhat.

I have had nothing but good results with matched manifolds (like Neal's and ours for the 250), just so long as the actual port exit isn't overly enlarged.