Help me out please?

[kw521]

i noticed this recently and I do not know if it is normal. but upon driving my car(usually at slower speeds 35 and under and im not fully accelerating my car seems to pick up and then slow down then pick up and slow down. It seems my turbo wants to boost then it doesnt. Is this normal when going to stage 2 with a tune? Could it be a vacuum leak of some sort? When driving normal at highway speeds I do not notice it. And when I get on it the car goes like it always does. This is driving me crazy trying to figure it out. Any help would be greatly appreciated!

[Reuben]

They do that, i've chosen to ignore it, and think of it as the car telling me to not be a panzy and driver properly. I have an Old school 90's STi ecu though, it's either on or off, and the transition between is a bit messy.

On a serious note, as in the other thread, o2 sensor or AFM may be playing up.