There is a test port on the 3.2 fuel rails - left rear corner of the rail (closest to cylinder 1). Factory puts a ball inside then a cap.
I plan to screw my sensor in there, then run the electrical wires back to the ECU. From memory, its M14x1.0. I got a M14<->NPT adapter from a local hydraulic shop.
Saw your thread on Rennlist - are you sure its the FPR?
87 930 K27HFS/B&B/Twin-Plug... Megasquirted