I recently replaced my fuel pump and ever since, the car doesn't seem to run quite right. I just checked the fuel filter and blew out all the lines and it seems to run a little bit better. However I'm getting a fair amount of backfire flame out the carb when I rev it up. Should I just replace the air filter and test drive the car, since that should not allow the flame to catch, or should I try to figure out what is causing the backfire first? I haven't changed anything else on the car like timing or plug wires and it ran great before the fuel pump went out. Also, the car hasn't been run in several months.