Hello everyone! I have a 2004 MC ss supercharged. I had to replace the valve cover gaskets recently because they were leaking oil. While doing so I figured it was a good time to do the upper intake gasket too. I did both, threw the engine back together and now it misfires, stalls when first starting, and has a loud squeal that I believe is a vacuum issue. I found out that I did torque the bolts properly and some rad. coolant leaked into the intake. I re-torqued them and the leak stopped. However the misfiring and squeal stayed. The only code I get is a P0300. It has new plugs and wires replaced in March, new fuel injectors, new gaskets now, new tubing for the vacuum lines, and a new pcv valve. I can't figure out what is causing this and am lost on what to do next. Any help would be much appreciated! Thank you everyone!

Edit: the misfiring only happens below roughly 2000rpm. Once its over that its got all the power and running fine except the squealing sound stays there.

Link to video of the squealing sound: