rushlow87

So iv been building my motor for the past 9 months and I just put it in my car and when I turn it over it sounds like its backfiring through the intake sometimes.also I have a 2000 LS1 head and another 97-98. I had a helll with the valve cover and vacuum issue.then I realized that the 97 head had a knotch cut out where it boltd up to the block.I found this out when I filled up the reservoir with water FML. so I pulled the driver side head off and saw that cylinder 4 and cylinder 8 where not firing at all. I know that I did the timing right because I know you just line up dot to dot. it's not throwing any codes besides temperature sensor codeI know it's not a bad ignition coil or bad fuel injector so I'm thinking maybe it's the PCM. any advice would be helpful anything at all please guys I'm just sooo bumed about it. tomorrowI'm going to pull the plugs out on the passenger side and see what cylinders are not firing on that side.