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A few people have asked what VTEC controllers are, and how they affect the engine. A VTEC controller is basically just a RPM activated switch that connects to the VTEC control valve and switches cams at a pre-determined engine speed, rather than letting the ECU figure things out. I have reverse engineered a commercial VTEC controller to see how one works, and found that they also look at the oil pressure and water temperature sensors like the ECU normally does, so that the cams are not switched if something is wrong. I have heard of people using an off the shaft rpm switch as a VTEC controller.

VTEC controllers are useful if the engine has been modified, and the ECU switches cams too early/too late, and for certain engines where Honda has got the cam switch point wrong. The only example of this that I know is the VTEC prelude, which has a huge jump in the torque curve because the cams are switched too late. Rumour has it that Honda did this deliberately to get a good EPA gas mileage, but there definitely are benefits from getting the prelude to switch cams earlier.

With the stock B16 engine this is little to be gained from changing the cam switch point - the ECU does a much better job than a VTEC controller because it can compare the torque curves of each cam and switch where they overlap. If you need a VTEC controller then it will be evident from a jump (up or down) in the torque curve when the cams switch. This may be difficult to judge even from a dyno because the cams should switch at different speeds with different engine loads, but a dyno print out would be the way to check.