3406E warms up looses boost ?

[Rockyhill]

So I’m the owner of the truck in question so far I’ve changed the intercooler, all fuel lines are brand new turbo is good, I’ve ran it with the waste gate plugged off the air and fuel sensors on the motor have been changed the three little check/relief valves in the filter housing has been changed new fuel pump I have a fuel pressure gauge plumbed into the cab it runs around 95 psi when driving down the road had the rack ran recently at caterpillar always service the truck at around 250 hrs the truck will spool quick and run about 25/27 psi for boost in the morning but as the day goes on it becomes slow at building boost and will only build about 15/18 psi of boost it seems to be worst on warmer days I have another mechanic thinking one of my injectors might be bad as it gets hot we’ve had it on a laptop all the fuel pressure runs at desired when running down the road also it only acts up after going down the highway after about 20 or so miles and when I stop to get loaded again it will be ok till I’m on the high way for a bit