Check the Catalytic converter
Had the same problem with mine. When under load it would “scream” and no one could figure out why, even was producing codes for cylinder #3 had multiple misses. Changed the belts, tension rollers, pvc, also changed the plugs and other ignition componets. when we were at Elkhart this year we stopped by the Ford Dealership that provides the chassis to Thor. The mechanic starts the engine and says the catalytic converter was bad/clogged and causing back pressure to the manifold and leakage. The “screaming” was from the manifold leakage. Replaced the catalytic, repaired the leakage, ....4,000 miles no more chirping, or screaming.
So check the catalytic and manifold leaks first. Make sure the tempature going in and tempature going out is close.
2014 Thor Challenger 37GT