questions about 2004 5.3L Silverado Z71 engine.

I've read a few forum conversations on here and got some good advice and
information on how to fix my issues. After looking at my engine and trying to
apply the new learned knowledge, I have learned my engine is not the same as
I previously thought and after researching engine diagrams of 5.3L. To get to
the point, my truck is having running issues. It'll start (after acting like the
voltage is low and resetting the radio clock), but after getting on the road to
work 3 miles away (5 min drive) the truck bogs down and wants to stall out
unless I feather the throttle to keep the revs up. This all started with this
Indiana heat 90+ degrees, I thought maybe it's starting to overheat, maybe
there's air bubbles in the engine. I drained the system and replaced the
thermostat and refilled the system. Still acting up. Then I came here and read
information about the same problems and *John Saffrahn* gave great advice
and knowledge. went back to my truck and found out I DO NOT have the Fuel
Pressure Regulator on the left side on my engine. So this is my problem, I need
help with the technical identification on my engine as well as help diagnosing
the problem. please help guys! I will appreciate any advice.