Heres the problem. When I get in my blazer in the mornings I have to accelerate slowly or the motor backfires thru the carb. A little gas and it runs fine but alot and it backfires. When it is warmed up it doesn't do it as often. Other times I can stomp it and the thing kicks in like it is suposed to. I have a 350 with a 4bl quad. Whats causing it and how do I fix it.