I just put in my new motor and I started it up and it only runs a few secs and then dies.
The motor is setup for NS, do I need to mess with the PFC or could i have a vac leak???

 

Check the link that has the various vac setups... Seq, NS, Parallel, etc.

I've got a similar problem, and have been about one incident away from ripping every fraggin vac line out and doing a complete vac reduction.

If you're running NS, that's the way to go.

A way to check this is by starting the car, letting it idle a little (torque down the idler screw so that it forces the car to idle for a bit - kinda like holding a tiny bit on the accel), and spray starting fluid around nightmare central (vac center under the UIM and/ or any other place that's suspect.

Once that crap is sucked in, you'll know immediately due to the idle change.

 

something may be causing power to the fuel pump to be cut

make sure the resistor is plugged in properly

if all the wires and plugs check out run a hot wire to the fuel pump from the battery and see if that works. easier thing may be for you to actually verify fuel pressure but that's my 1st bet as to what your problem is.

 

Well the car seems to run a little longer when I give it some gas...

 

Car starts immediately because you turn the key and the pump comes on but as soon as it starts I'm guessing the pump is shutting down for some reason, verify this with a fuel pressure test. Sure if you give it gas it may sputter another second or three

Or as mentioned simply run a hot wire to the fuel pump forcing it to continually run.

Or it's something else entirely but that's my 1st stab in the dark.

 

Was the old engine non ported, and now you have a ported engine? That would cause you to run off differnet cells in the PFC and could be causing you to lean out as well. More info on your setup please.

 

Non ported engine
PFC
fmic
3 bar map
walbro pump
haste 3" rad