Misfires at about 40mph espcially uphill, runs ok otherwise

I replaced fuel filter.
I get no trouble codes.
I have checked all the grounds and battery voltage to the FPDM under load and all are good.
Putting a screw driver to the fuel injectors and listening to them, they all seem to be working ok. The resistance measured at the injectors are at specification.

I checked fuel pressure: koeo I turned key on and off several times, each time the pressure would rise - started at about 10psi and went up to about 40psi or so. The voltage across the fuel pump from the FPDM is about 10.8 V DC peak value on an oscope, with an average value of about 8.5 to 9V DC read on volt meter. Manual says that the pressure with engine not running should be 50 to 85 psi. If I put the battery across the pump motor I do get 53psi.

At idle I get about 33psi, and if I rev the engine this goes up. The voltage at the pump is about is about 8.5 to 9 VDC with meter. When driving on highway the voltage goes up over 10 sometimes. If I remove the vacuum from the pressure sensor the pressure rises.

Chilton manual says that if the KOEO voltage to the pump is over 10.5 volts or so and the pressure isn't at specification replace the pump. If not the problem is elsewhere.

So my problem is should I replace the fuel pump since the engine off pressure is not at specification unless I put battery right across the pump, or should I try replacing the FPDM since it doesn't seem to be putting out voltage specified by Chilton. Any advice or suggestions are appreciated.