2000 Impala LS 3.8L V6 P0300 Multiple Random Misfired has me Baffled

Right, I’ll have to replace the gaskets but for now there is no vacuum leak. I have stopped trying to start it because it backfires up through the intake hard enough to blow a vacuum line off and I don’t want it to crack the intake. I need to find out why it is running out of time and running so rich.