I have a 2009 1500 with the flex fuel 5.3l that has a rough idle and a strange intermittent knock of a sort. The ‘knocking’ seems to coincide with the RPM and it’s generally rough idle. The knocking goes away under load and has no issues running, in fact, it runs great other than idle. So far, I’ve replaced plugs, wires, changed oil, cleaned MAF. It has the occasional P0172,P0175 code combo and hard cold start but I’m pretty sure that’s just linked to the bad alcohol reading. I don’t have an advanced scanner to reset the alcohol content so I’m just driving it in the hopes it’ll clear itself after enough fill ups. I just need help in getting steered in the right direction for this knock though. It’s fairly concerning. Here is a link to a YouTube video of the noise