Ever since I changed the engine in my au falcon it's had this problem whenever I take off foot down past half acceleration the car will either stall or rev really rough untill I take my foot off but if I accelerate slowly it does it less often I recently had the gas put back onto the new engine and it doesn't stall at all does anyone have any clue what it might be ???

Blocked injectors possibly, but more info req. what else was done when the engine was replaced?

clogged fuel filter or bad fuel pump??

When the engine was replaced everything was checked and put back together recently had full service new radiator new power steering pump the throttle body was changed to actor for the gas system other then that it was a perfect swap it feels as though when you put your foot down it either gets to much air not enough fuel like it feels like it wants to stall but as soon as I released the accelerator it goes back to normal