hard cold start/ lack of power

[pkupman03]

I first noticed the problem when i was towing my RV up a long steep grade. I started the grade and slowly pushed the pedal farther and farther but wanst picking up any speed. Trans would downshift until the pedal was to the floor. i eventually was going 15mph up a grade I could usually go 55. there was NO smoke, egts never went over 850 and cooland temp was normal. Boost slowly dropped and wouldnt pick back up. It just wouldnt go. I pulled over, and set my truck back to stock (have sct livewire) and took off again but same problem. I eventually made it to our campsite and unhooked the trailer and drove the truck. It ran ok but had a miss the would come and go. Best I could describe it was it sounds like an engine on the rev limiter "Pop Pop" I havent got any codes, no check engine light. Replaced the egr valve, changed the oil, both fuel filters, did the "blue spring" fuel pressure upgrade spring and added a low pressure fuel gauge. Air filter is clean. Just checked FICM, key on 48.6v, running 48.6v. It runs worse cold than hot. Cold it almost wont get out of its own way. Oh and with the SCT livewire on haul *** mode its not as bad but with it tuned back to stock it has NO power and does that "pop pop" rev limiter noise when its cold. Twice early in the morning it wouldnt start on the first try, but cycled the key again and it started. Im thinking HPOP or bad injector/s? but no codes. Also i noticed when i turn the key on and the injectors do their buzz thing, id doesnt seem like they buzz very fast, compared to other 6.0s ive heard.

sorry for the novel just trying to give everyone as much info as possible. Thank you

03 f-250 4x4 175,xxx miles
SCT livewire
K&N cold air intake
4" turbo back exhaust, no cat/muffler dual exit, 8" tips
"blue spring" upgrade
6.4 banjo bolts
auto meter boost, EGT, fuel pressure guages
05 trans