Van wont start during cold weather.

I have a 1998 GMC Safari with about 150k miles. For the past two years my van will not run when the outside temp. drops below 45 degrees F. When the weather warms up the engine cranks up and runs, but there is misfiring. I changed the fuel pump, fuel filter, ignition wires, cap & rotor, and installed Bosch platinum 4 electrode this past summer. Yesterday I experimented with a new ignition coil, engine coolant temp. sensor & air temp sensor. The van just wont start. The fuel is about three months old now. I tested the fuel pressure with the engine off and I get a spike of 63 psi followed by a steady pressure of 58 psi. After three minutes my pressure reads 52 psi so there may be an injector leak or something. I noticed that this model did not seem to like the Bosch Platinum’s 4 electrode plugs which seem to get doused easily, so I was think of going back to the original AC Delco single electrode platinum plugs. Any suggestions on where I should proceed to tackle this monster. I don't know a whole lot about cars, but I really do want to get this van working? Thank you.

Be sure to use only A/C Delco Plugs, Cap, and wires.......all others may be the problem