No, I think you've got it back to front.
I think ACIS works as described below, but anyone can feel free to correct me.
With the gen2 3sge with the motor running,
below 5000 rpm the ACIS valves are closed, making the intake runners operate at
full length (from the valves out to the throttle body - long runner - max torque).
A bit above 5k rpm the ECU starts to open the valves, effectively making the runners operate at
half length (the lower half) for max power at high revs. Something called Helmholtz effect and I can assure you that ACIS definitely works.
Shortly after I bought my car I discovered that the ACIS valves were seized up. Water had got past the metal gasket into the middle hollow inside the casting and badly rusting the shaft. (keep this in mind if washing down the motor after degreasing)
It was impossible to free it up and I had to replace the whole ACIS assembly. After that it sure made a hell of a difference at high revs, and I could really feel the rush just over 5k.
To test that the shaft is free you need to carefully reach under the operating lever and check that it moves freely, but the service manual gives a full procedure for testing ACIS operation.
post edited by Reddtarga - 2013/01/04 17:11:20