ACIS PowerDeck

Long story short, the ACIS works like this, first you have the top intake manifold (17129), intake chamber/bulkhead (17300) and bottom intake manifold (17111).

http://www.toyodiy.com/parts/p_J_1990_TOYOTA_CELICA_ST183-BLMVF_1701.html

The (ACIS) or Acoustic Controlled Induction System increases the power output at all RPMs. The intake manifold has a built-in adjustable bulkhead (door) that divides the intake manifold into long and short tube lengths. Using an intake air control valve, this bulkhead is opened or closed depending on engine RPM and throttle valve position. Long-intake runners are used below 5,100 RPM with short runner lengths being used above

In low rpm operation the butterflys are vertical... there is a small gap underneath them allowing for just the bottom half of the intake runner space to be used, the rest of the vacuum sucks from the empty chamber you've just enlarged. Now you've also opened up a path that was once a dead end to allow vacuum to suck over the top of the butterflies and through the top half of the intake runner space effectively removing ACIS operation. Now you've lost mass amounts of low end torque and will not have gained anything up top. you can prove this by zip tieing the actuation lever you'll notice the 3S-GE bogs down if ACIS is open too early in the rev range.

To add a bit more BHP, you can get a powerdeck spacer. This is basically a spacer that sits under the intake chamber creating more air.

Much easier to read this thread:

http://www.6gc.net/forums/index.php?showtopic=69297

Only down side to this is that it makes the engine run lean, will post up a link and show the figures.

Here is the powerdeck spacer aswell

http://www.nengun.com/top-fuel/power-deck-spacer

hmmm, would love to see some dyno figures, i would imagine it would rev well

im still trying to find them IIRC, it was a 'noticable' difference