lost my book; what is code 327?

Exhaust gas recirculation valve sensor circuit below minimum voltage.

Possible causes:

Damaged EVP sensor.
Damaged EGR valve.
Open harness.
Grounded harness.
Damaged Powertrain Control Module (PCM) .

most likely the evp sensor is bad. however if you buy a new or remanufactured egr valve at your local auto parts store it will come with a new evp sensor on top.
the evp sensor is the auctual part that has the plug and is bolted to the egr valve with 3 bolts

http://www.allfordmustangs.com/Detailed/445.shtml

For future reference