There are a aftermarket manifolds for the K03/K04 series, but your best bet would be to get the factory manifold ported. $300 vs $700-800.

If you would like more information, send me an email.

for the K03 and K04. They claim it will make an additional 10hp.

Ken Huggler

RUDE. I politely asked them for information and I recieved a response that practically flamed me for asking. "WE DON'T CARRY THEM ANYMORE"

how does TAP stay in business?

Ken

You can just go and bore it out to the max because that would actually have a negative effect on flow. The increase is usually small but it's secondary function is smoothing of the inside of the manifold to reduce turbulence.

thermal cycling on thin metal generates stress wall fractures...
an exhaust manifold isnt very useful if a chunk has cracked off =/