2001 4.6 V-6 hard start

I have a 2001 Chevy Blazer LT 2 wheel drive V-6 4.6 Vortex and about 6 months ago the truck became hard to start after it had sat for 7 hours. We had to replace the brake booster and after that was when the starting of the truck issue began. When the truck is started first thing in the morning it takes about 15 tries before it will start. It sounds like it will start but does not want to kick over. You can hear the fuel pump engage and from what i was informed the fuel pump was replaced. When we bought the truck you could smell gas real bad and we ended up having to put new gaskets and seal the tank properly because that mechanic was not smart. Afraid i would flood the truck i am weary about pumping the gas pedal but you never smell gas when you try to start it. We have replaced mass air flow sensor, plugs, wires, distributor cap, rotor and finally the fuel filter. I am at a loss. Last week the codes P0174 and P0171 popped up that was when we changed the fuel filter. Yet truck still is very hard to start in the morning. Any suggestions on what to check? I am at a loss of patients and money on this truck.

What is your fuel pressure? How long does the pressure hold after turning the key off. Does pressure build rapidly on the first key cycle? Try cycling the key 2 or 3 times before engaging the starter. This will allow the fuel pump to go through the prime cycle 2 or 3 times to build pressure.

Check for a vacuum leak.

the pressure is at 45. finally able to get the truck to start but the only way is by putting starting fluid in the dash pot. if truck sits longer then 5 hours you have to use the fluid again.