I just bought this truck and it runs as if i were pulling a trailer. I had it troubleshot and it threw codes for the mass air flow sensor, o2 sensor, and cylinder 4 misfire. I replaced the spark plug in cylinder 4 and nothing changed. I switched the coil from cylinders 3 & 4 and then it gave me the mass air flow and 02, but the misfire went from cylinder 4 to cylinder 2...please help.