We had a client with a bone stock 2006 WRX come in for a base line. He told us he had something he wanted to try out, and we said great. So he did his mod, not telling us what it was and we put the car back on the dyno a week later. As you can see from the graph, just the extrudehoned intake manifold was worth a peak whp of 16, and peak wheel torque of about 8. But aside from peak numbers, the area under the curve has increased dramatically. Power deltas across the rpm range have increased as much as 20whp and torque at certain points. I think it is safe to say that the ported intake manifold is worth a solid 5-10% increase in power.

Red Run number 2- Bone stock 2006 WRX
Green Run number 2- Same car but with only the extrude honed manifold
Black Run number 8-Same car tuned at 16psi.