Scotty, I replaced plugs and injectors that I got cheap from Ebay after it was giving me a P303 code, misfire 3 cylinder.  About 3 weeks later started getting a P0172. A mechanic did diagnostics, told me it was running rich suggested I replace MAF, and both 02 sensors.  Still got the code.  Replaced fuel pressure regulator and CTS.  Didn't help. Took it to another mechanic.  He found the my EGR was bad, replaced it but still getting a code.  Suggested I replace the ECM.  I read that ECM's hardly go out on this things so I disagree for now.  Took it to another mechanic, he had no idea but didn't think its the ECM.   Suggested I work backwards with all the stuff I replaced.   Happened to pull the dipstick to check oil and it looks thin and smells funny. Level seems to be a little high.  Could my injectors be defective and leaking sending gas down into my crankcase??   I'm thinking of changing the injectors again.  Out of ideas.  What do you think?