why would the PFC cause you to fail instantly? im fairly certain having aftermarket engine managment is not a breach of an EPA guideline, and also having an aftermarket turbo doesnt mean "your gone"... i think your getting just a little too worked up...
when you go to the EPA place, they pop your bonnet to check PCV (possivite crankcase ventilation) hoses, then stick a probe up the ass to check emmisions, im pretty sure its done on idle, acceleration and deccel, its not that hard to past as your car isnt under anyload (its free reving) so it shouldnt be pissing that much fuel in anyway... then they take it 20m up too a open area and do a noise test, now they test your car at 3/4 of peak power (so for a skyline i could imagine about 4500RPM) and they also test for decelleration noise output aswell, so any burble or backfire will get caught out...
to pass, put a standard exhaust on, and a standard air box with standard filter, make sure the PCV is connected and turn the boost down and have sum1 tune the PFC to suit...
n if u are really keen, heat wrape ur cat, with some off the shelf heat wrap stuff from ur local auto store (raising the temp of the cat, burns off more nasties but shortens the life of it)
EPA is not that hard, just a bit of a headache, dont go forkin out all this cash to go back 2 standard etc, im pretty sure if u fail u jus have 2 get retested... but you only have a month before your rego is suspended, but the EPA's number will be on the forms you recieved in the mail, give them a call....