1998 V6 chevy S10 fuel pressure regulator diagnosis

[STRAYDOG]

Still need help on my V6 S10 with TBI , no start after sitting overnight.

If I disconnect vac line to fuel pressure regulater & apply vacuum.....it wont hold any vaccum & no resistance ............. note if i do same thing to wifes fuel pressure reg & car runs great ( 2003 v6 pontiac) it holds vacuum .........is my problem the regulator ??? thinking should i replace before being towed to chevy dealer it used to start if i held throttle to floor whille cranking ..... help fuel pump OK & have changed filter ............ any way to diagnose if itds the regulator