aftershock00

I have an 01 5.3 with about 105k miles. For the past month or so, I have noticed that the truck doesnt instantly start up with the tap of a key like it used to. It cranks for a few seconds. At first, it seemed like this would only happen after the engine was warmed up and then sat for about an hour, but now it doesnt seem to make a difference when I try to start it. Once it starts, the motor runs relatively normal and gas mileage is average.
I noticed that the truck will start right up if I turn on the ignition and wait a few seconds while the fuel system/pump primes
and then I engage the starter.
I read through many forum threads and I changed the FPR with one from advance auto. No change. I changed the fuel filter about 6 months ago so I dont think thats the problem and I changed the fuel pump about one year ago with an AC delco "updated" pump from the chevy dealer. Because it starts faster after being primed/represurized by the pump, im thinkin its a fuel pressure problem.
I dont know where to look at this point. I dont have a pressure gauge btw, but im going to take it to a mechanic in a few days if i cant figure it out.
It may be worth noting that when I put the key in and turn the key just enough to start the pump, the whine that the pump makes changes tone half way through the three second "prime". I dont recall it doing this before, but who knows at this point. The pump always made some type of "whine" since new, but it was a consistent one.