I inspected the exhaust run, and no rattling bits when I shake it. Also no screen at the end on either pipe. It's a 1993 e350 chassis turns out. The belts are 6-groove, not v on both the alternator and the main drive belt.
The exhaust system had slipped a rubber clamp about midway along, and was resting on the frame about an inch lower than it should have been. I braced it up and regung it, looks ok now and less whistling.
Still suffering from very little power at high RPMs and late shifting when accelerating or going uphill
Pulled the PCV valve and it seems ok, rattles nicely and actuates with no resistance or sticking
