Yeah thats normal, i'm not even sure if mine makes full boost in 2nd would lose traction first!!
Because it's a lower gear the engine is under less load/stress and so doesnt flow/breathe as much as in higher gears, bit like cycling a bike up a steep hill in 1st then trying the same hill in 21st gear! Your legs wil be under a lot more stress/load so you'll be breathing heavier lol ........same goes for your engine as you go up through the gears.