Does this seem like a logical explanation to less power output?

[larson]

Ok so once I start up my truck and let it get to operating temperature the first 10 to 15 min of driving it hard seem to yield really nice strong acceleration at full throttle. Now after driving it for an hour or so continuously going to or from work it doesn't seem to have near as much snap or seat of the pants feel.
I have noticed this for awhile now but wanted to wait and see if it was just psychological but its like this every day.
My entire fuel system has been replaced(almost). Damn near new except for the IP having been replaced about 35-40k miles ago but still new enough. BUT my injectors are original OEM with 180k miles on them. (they are worn out) could this be why the lack of power once driven for a while? New injectors are next on my list. (c-mass bonus purchase). The truck runs fine as far as daily commute goes I guess I'm just asking this out of curiosity not out of a help me situation.

New fuel parts include everything from fuel lines from the tanks to new lift pump(mechanical) to damn near new ip.
As stated above new injectors are next on the list. Also all return line hardware is less than 10k on top of motor and any lines going back to the tanks were replaced in the last year.

 

[79jasper]

It's the timing advance.
Replace the injectors and time it.

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[Clb]

Ok so whats actually "new" (replaced you said)???
Ip's and injector lifespan(serivce interval) is 100k
Heat soak, and warm internal seals leaking could cause your issue.
Bet santa cures this problem.
Hit the stickies and do some homework.

 

[icanfixall]

I too "feel" this phenomimom sometimes. But you injectors have run their useful life out some time back. If you replace the injectors I suggest you advance the pump to the next setting you made because the new and not rebuilt injectors are going to be popping later because of the higher pressures compared to what you have now. Old injectors very seldom will pop at the 1850 most injectors like. The pressure fails over long useage and that normal. Its just a spring that weakens over time.

 

[larson]

Ok so whats actually "new" (replaced you said)???
Ip's and injector lifespan(serivce interval) is 100k
Heat soak, and warm internal seals leaking could cause your issue.
Bet santa cures this problem.
Hit the stickies and do some homework.

Everything except the injectors has been replaced. The ip would be the oldest of all the replaced fuel system parts having around 40k miles on it. The truck has been timed with Gary's Kent Moore equipment. It's set to 8.2-8.4 off the meter reading.
As stated already once warmed up the first 20 min of driving it it pulls very nice with black smoke blowing out the exhaust in just the right amount considering the ip is NOT turned up at all and then it just seems like it's not as powerful after driving it for an hour or so if I get on it full throttle again hardly any black smoke.