I haven't been able to locate a drawing/photograph of the sensor, but the following excerpt from the 1996 Cougar PC/ED manual and Service Manual may help you to locate the PF sensor. From what I read, it's somewhere along a fuel vapor hose that connects to the EVAP canister:
HW18 CHECK EVAP CANISTER PURGE VALVE STUCK OPEN CONDITION OR PF SENSOR DAMAGE
Disconnect fuel vapor hose from intake manifold at PF sensor.
Reconnect the EVAP canister purge valve (electrically).
Install a hand-held vacuum pump to intake manifold side of PF sensor.
Apply 53 kPa (16 in-Hg) of vacuum to open end of PF sensor.
Does the EVAP canister purge valve-PF sensor assembly hold vacuum for 20 seconds?
Yes
LEAVE the vacuum pump connected. GO to HW19 .
No
If PF sensor housing is cracked, REPLACE PF sensor. Otherwise, REPLACE fuel vapor hose between EVAP canister purge valve and PF sensor. If fuel vapor hose was OK, REPLACE EVAP canister purge valve. RESTORE vehicle. GO to HW42 .
HW19 CHECK HOSE BLOCKAGE - EVAP CANISTER PURGE VALVE STUCK CLOSED CONDITION
Connect scan tool.
Apply 53 kPa (16 in-Hg) of vacuum to open end of PF sensor.
Key on, engine off.
Access Output Test Mode on the scan tool to cycle EVAP canister purge valve.
Key off.
Did the EVAP canister purge valve open and vacuum reading on the vacuum pump drop (air passes freely) when commanding the output on?
Yes
REMOVE vacuum pump. GO to HW20 .
No
REMOVE the vacuum pump. REMOVE blockages in fuel vapor hose between EVAP canister purge valve and PF sensor. If OK, REPLACE EVAP canister purge valve. RESTORE vehicle. GO to HW42 .