4x4chevyrig

Hey guys I’m having an issue with my pickup. She squeals like crazy under load/gas. Starts to misfire at 3500 and won’t rev past 4000 rpm under load with next to no power/losing speed at that point. Told intake manifold (has thrown MAF a few times but not consistently and did clean it) also heard cam bearing. Truck drives perfectly fine minus squealing below 3500. Not quite all power but still moves fine. Any ideas?