Stuttering until Idle

[2GSOCAL]

When its cold out (frost on window), i start the car up and it idles fine. When i take off however it putters and wants to die, i have to rev it up past about 3k and then take off while keeping it above 3k. This only appears to happen in 1st and 2nd gear, another symptom is while this is happening i can floor it and it does nothing for a second or two, then it just takes off full boost. It seems to be fine when it reaches operating temp. Also when i hit max boost in 2nd or 3rd gear sometimes right before i go to shift around 5k or 6k and im WOT i hear a release of air and the car misfires or something and just stops accelerating, its like a thud like when i blew off my lower IC hose before. But everything is fine after this noise, i just let off the gas and continue on, when im at WOT in 4th and 5th and max boost this hasnt happened yet. Any ideas? I just got the engine rebuilt about 400 miles ago and it has a new EVO III 16g, with boost controller set to max at 15-16psi. Might it be fuel cut? I dont have any type of aftermarket fuel pump or FPR. Any help would be appreciated. Thanks!

 

[2GSOCAL]

and just to clarify, the misfire or whatever it is at max boost in 2nd and 3rd happens at operating temp. I dont really boost hard before operating temp. But right after it reaches or after its been there for a while is when it happens, and it probably would happen in 1st if i boosted hard in 1st like i do sometimes in 2nd or 3rd but i dont punch it too hard in 1st unless its a standing take off, but it hasnt happened in 1st yet.