I've got almost everything figured out but not quite... the BAC- what does it do and what happens when you remove it? Also, i have both jdm and usdm upper intake manifolds- what is the thing just above the BAC on the usdm and why is it not on the jdm?

 

The BAC valve is nothing to do with emissions, it's the main idle control valve.

You lose idle speed control.
The ECU uses the BAC valve to compensate for loads from the alternator, A/C compressor and power steering pump. If you have A/C or power steering you should definitely not remove it. Even if you don't, there's no point in removing it, there are no gains.

It's the solenoid valve for the accelerated warm-up system (AWS), the 3000rpm idle to get for a short time when starting a cold engine. This function is to heat up the pre-cat(s) as quickly as pssible to reduce cold-start emissions. Japan's emission regs were not as strict at the time so JDM FC's had no pre-cat and no AWS.