Yes, starting from Evo IX, the head got MIVEC already but in the IX only for intake side, while for the X if I'm not mistaken already for both intake and exhaust (CMIIW though coz I don't really pay attention anymore to the X). The MIVEC actually should make the engine more powerful and responsive.
What is CMIIW?? MIVEC used to be for high revving NA engines like the 4G92 MIVEC and 6A12 MIVEC. But recent new ones are more towards better fuel consumption like i-VTEC. For Evo, I think the MIVEC improves low end torque and fuel consumption.

