Weber trouble

OK,  I got the weber mounted and everything hooked up including the
choke.  Runs fine except when you put a load on it. Like if you would
want to drive the car.  Everything fine in garage rev's great, idle is
good, put it in first gear and head out and that is over.  Foot on the
gas and nothing except maybe a little bucking and back fire in the
carbs.  Any ideas this is a 40 dcoe on a 1098 with a mild cam.
                        Crash