The car started making the whistling noise which eventually became an intense kazoo sound, and it threw CEL codes 0171 and 0174. Yesterday I replaced the flame trap (thanking my lucky stars it wasn't an earlier model where the dang thing is buried), which took all of 25 minutes. I checked the old boy, and sure enough, the diaphragm was ruptured.

Fired it up and cleared the codes, then took it for a test drive. Within a minute the CEL lit up again with the same codes, but after I cleared them again they didn't come back. Then after a 20 minute drive, when parked at idle there was a new noise. This is more of an intermittent huff or cough, about 1 per second, which ceased when the dipstick was pulled or oil cap opened.

Any ideas? For the life of me I can't find any schematics for the 2008 and newer flame trap or crankcase ventilation system to see where else a problem may lie. The crankcase vent system was pretty easy to understand on the old red blocks - not so much now!