You can just ground the VTEC pressure switch input (D6). The switch just completes the path to ground if the pressure is high enough, so grounding the wire constantly does the same thing. Connecting A4 to D6 is the same thing; the other side of the VTEC solenoid is always connected to ground so that works.

The ECU apparently doesn't check the pressure switch once VTEC is engaged which is strange (because A4 outputs 12V when VTEC engages, which would make D6 go to 12V also).