Ok, put a holley double pumper 4160 on my ford 460, it's in a 1986 F-350. Has an automatice tranny and is 2wd. Truck idles ok in park, but when i shift into gear(any gear) the idle becomes rough and chopper and almost feels like it wants to die....once you hit the gas to drive it smooths out and drives ok, till i let off the gas to brake and it becomes chopy again....hasn't died yet. Any suggestions? Is it a vacuum leak or carb adjustment?