2000 LS2 v6 fuel problem?

I have a 2000 LS2 which I have just installed a new fuel pump and fuel
filter. Now the car is very hard to get started and keep running until it
warms up. Once it gets to operating temperature it seems to run okay. I
have 45 p.s.i. of fuel pressure now instead of the 32 with the old fuel
pump. However, with the old pump the car would not run very well for the
first 30 seconds, then it would run good except I could not pass anyone or
push hard on the accelerator without it misfiring and loosing power.
Seems like it is having a harder time with the new fuel pressure until the
engine warms up. Before the new fuel pump was installed, the Oxygen
Sensors were running open loop. They were also reading at over 1.0 volts.
Can you please help me with this problem?

 

Measure the fuel pressure under load and see what you get. Duct tape the
pressure gauge to the windshield.
btw - an old R12 refrigerant manifold gauge set is now worthless (unless you
have an EPA license). It just happens to fit the fuel pressure test port. I
use the low side gauge as 49psi is the target pressure.
You might also have to do a flow test to see if the problem is in a crushed
fuel line or something wrong in the fuel pressure regulator. On that last
one, make sure that the vacuum line from the intake plenum to the fuel
pressure regualtor is intact.

I've been going through all this on my 2001 lw300 getting a 'lean bank 1'
and 'lean bank 2'. Upstream O2 sensors read 1V (rich) and downstream sensors
read .7V (normal). Long term fuel trims are high. Points to a low fuel
pressure (dead-on at 49 psi) or vacuum leak but I haven't found one yet.
Thankfully, the friendly local service shop (not Saturn) lends me their
Snap-On diagnostic scanner.