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the ECU tuner for my skyactiv 2.5l with mistu ECU (also VVT/"mivec") offers aftermarket cams. They require a different ECU tune and 93 (USA) gas. I don't get why these guys do all this work and use a piggyback, when the oem mirage ecu is fully tunable. I'm guessing the know how is missing, because they could get a much more complete tune otherwise.
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I'm sure you could get an extra set of 3A92 cams and have them ground down for an 'economy grind'. Its just a matter of if you're willing to pay for it. :)
A performance grind is harder since you need more material on the cam lobe. There are places known to weld additional material onto the lobe, and then grind a new profile on it. This of course would cost more since its an additional operation.