weird power loss problem

[wayfastwhitey]

ok so i bought my 01 superduty in the early summer and it always worked fine and ever since it got colder(i live in canada) when i first start driving it until it gets really warmed up (have to drive for 10 mins or so) itll have no power until about 1/4 throttle and it makes a sound like a whooshing air sound kind of and as soon as you get past 1/4 throttle it hits and takes right off and works amzing. anyone got the slightest clue?

[stoken262]

its your ebpv(exaust back pressure valve) perfectly normal for it to stay while driving until the truck warms up. its a butterfly in the turbo that aids in the truck warming up faster