You guys are really a sensitive lot. I never claimed my tune was correct as this is why I posted in the first place so please stop making stuff up. ...
My opinion, the tune needs a bit of work. I'd start with your fuel injectors and make sure that all the data is correct. You can get the part number...
2009 Sierra 4.8 engine, bone stock, 290,000 Km. Started running rough and set P0300 code. Scanner show misfire counter for cylinder 3 & 4 only. I had...