F150 Hesittates

first you need to scan it for codes and go from there

BTW.. welcome to ford tough

bet your fuel pump is getting weak , as well change your fuel filter, first then go from there

Could be a coil pack I think 99's had 2 coils on the front of the engine and later on switched to COP's like the 5.4 first I would scan the truck, then check the coils and fuel pressure and go from there

I'd check the PCV Elbow at the back of the intake manifold,
look for a pinhole in the rubber elbow that plugs into the back of the intake manifold. If that's what it is it's a dealer item about 48.00 trouble code to accompany that might be a P-0171 and P-0174 Left and Right Banks running too lean.
A temporary fix is clean the elbow (carefully) then wrap it with thin strips of Duckt Tape about 3" long.
Good Luck and let us know how you did.
Oh and Welcome to the forum.