after changing the front brake pads i notice a strange braking difference, when i just drive and then brake it's the same as before, only before a full stop it feels like not willing to stop at all (could this be the automatic trans, i was used of driving a manual car) but it does stop.
now the strangest thing, when accelerating and having an rpm +2200 it feels like i need more force to push it and then it goes in like it has no resistance...
(btw my power booster is hissing ordered replacement but delivery takes time to belgium)
also keep having rabs (brake booster?)

 

I'm betting when you replace it the problem will go away. Hissing is a vacuum leak, and with no vacuum you have a very hard pedal.

 

but then when i just idle or drive at normal rpm is have a soft pedal? due to vacuum leak? maybe i noticed because i changed the brakes and had my attention on it. sure hope it is like you say