Here is my experience my mate and i both had
tercels one had 3ac and i fitted a 4ac in mine.
the biggest broblem i could find to air flow
was the air cleaner lid sits to close to the top
of the carby the secondary opens but can't get
enuf air in plus to small an air filter.My sulotion
after lots of looking was to fit a nissan bluebird rwd
air filter one the same diameter as the 4ac but is about
an inch higher take out the rubber sealing strip in your filter case
space up the bolt at the top of carb with a washer or to
so u can still screw the top on.u have now spaced the air
cleaner lid away from the carb and have a bigger air filter
pluse opened the case up all around the bottem of the lid
= lots more power and cheaper air filter then the toyota one :) give it a try worked on both of ours