i have a 79 malibu with a 267 and whenever i stop at a stop sign and then go forward i hit the gas and it stumbles and cuts out as if its not getting fuel.a few times it actually killed in the middle of the intersection. it also backfires through the carb. was wondering is this a timing issue or is the carb junk. its the half moon two barrel. accellerator pump maybe? any answers would be great thanks casey