how to exactly test fuel psi

[dastang2]

hello i searched and did not find what i want to know. do i have to test the psi with the vacuum line off of the reg. or on. with it off i got about 38 idleing and revved. with it on i got 28 at idle then revved it went to about 38 and shot straight down again. is this a bad fuel pump.

 

[dastang2]

hey i found out that the car has a bad fuel pump, it got really bad last night and wouldn't climb a hill so i tested the psi right then and when i revved the motor the psi dropped to 5 psi