2000 LS 3.9 v8. It started out with just the 0304 code last week, so I changed plugs and COP's($400). Still running rough. All the injectors are getting power signals. Also, 2 months ago, I had to repair a cracked fuel line at the elbow connecting to the inlet side of the fuel filter. Changed the filter too. haven't checked fuel pressure yet going to get a tool later maybe. I've never messed with fuel delivery systems much, so it's new to me. Am I going the right direction?