its not so much about gain with the 007p, it`s just that the ECU/engine preferes them. the car should run smoother with it.
i doubt its the dump valve causing the delay though it would be a factor i suppose

i do find myself that when in second at about 5-10 mph it`s not got enough grunt to pull. you would want to be in 1st if you want a fast pull away from that speed, other than that, like i said, give it some revs and ride the clutch a little, but thats not good.
personally i think you just need time to get used to the car.