2001 Safari Will Not Start

I am having a starting problem with my 2001 Safari 4.3L V6. Parts that have been replaced so far include: Battery, Fuel Pump, Fuel Filter, Cap and Rotor, ECM, Coil. Even with all of that I have fuel pressure, and have checked that the plugs are not fouled, and it still will not start. It turns over, but never makes an attempt to fire. No partial start, nothing...Checked for codes and there are no codes showing. I am now at a loss for what could be causing the problem. Any help would be greatly appreciated. Thank you!

Can you test for spark at the plugs?

We have pulled one plug from each bank to make sure they were not fouled and to test spark....we get spark. We are just completely lost on what could still be causing it not to start.

Can you test the fuel pressure to be certain there is at least 58 PSIG? 56 won't get it done - It's that critical.

I don't have a fuel pressure test gauge, but I will check with a friend who does and find out for sure.