g-16 carb question! need help!!!!!

[kwh3rd]

I have a 99 g-16 and have the plowman's high perf clutch kit and the custom pipe and muffler. I had the k&n air filter and did the mod to the air box but it wasn't enough so I installed a UNI pod filter and it kicks butt. My problem is that every once in a while it back fires and it sputters on take off. No matter how much I adjust the screw with the spring behind the carb it doesn't seem to help. I am not sure if the needle in the carb can be adjusted or not. If it can should I move the needle up or down. I have the bigger jets in it that I got with my kit from plowman's. I don't want to go back down a size in jets. I think Its just a problem with adjusting the carb. Like I said I tried everything and every position that is possible with the screw with the spring in the back of the carb. Please help.