PFE sensor 1989 Cougar LS

I had an idle problem with my cougar (1989, 3.8) that was solved with the replacment of the Idle air solenoid (IAC). The dealer also told me that the PFE sensor was reading erratic voltage and needed to be replaced. Could the bad IAC have been causing the PFE sensor to be reading bad or should I still replace it. Also where do I find one, I have not been able to find it on the web (rockauto.com, etc.......) or at the local auto parts houses.... Thanks (in advance) for any help.