Get intake, exhaust, short shifter..
It's not a mod unless you get a more efficient one because an automatic transmission has to have one.
a torque converter that spins your tranny at idle a little faster may help a little...but it has no performance gains whatsoever as far as i've learned.
It wouldn't matter how fast it would spin it at idle because it only has to spin it fast enough in order to keep the engine from dying. It kinda acts like a clutch in the sense that it connects the engine to the drivetrain so it works at idle to keep the car from dying, and it also works when you accelerate to a certain point and then things take over from there. A torque converter also multiplies power created by the engine and transfers it to the drivetrain, so a more efficient one will transfer a little more power of could possible allow you to rev higher as stated in the post above, but I thought that was controlled in the ECU? I don't know much about the autos but I know that the manuals won't let you rev past a certain point without the clutch disengaged, although that's what I read, never tried it.