ok heres my problem My 2001 silverado started out life as 6 banger but now has been converted to a 5.3L. The truck keeps giving me a code for random missfire when on the highway or wot, when i check to see what cylinders it is it shows 100s of misses on each cyclinder. The thing is my 6 banger kept giving me this code before i replaced it with the 5.3l. Im lost at where to go Ive changed the fuel pump, o2s, stock mass airflow to a grantelli mfs and high flow cats. Both motors had headers, cold air intake, free flow exhaust and nelson tuned computers. ANy help or ideas would be great. Thanks