On my variant of this model, I included a switch so that the chuff/no chuff could be turned on or off. A small slide switch was mounted discretely on the side of the case. The noises heard with anti-chuff mod implemented are to do with the native 1 kHz base frequency at which the PLL circuit operates. It generates a lot of phase noise as one makes frequency steps, until the PLL lock stabilises again. IIRC it is not so noticeable on quiet bands, but acute when tuning on strong signals.
The whine, I remember well enough. I seem to remember curing it with better shielding between the CPU/controller board and the ferrite rod antenna. It was a long time ago since I made that mod, so details are a bit sketchy, but it did involve digging quite deep in to the radio, removing the RF board.
Once, just once I was able to get the set to do something weird and neat that I have since seen reported elsewhere. With some odd combination of battery change and application of power, it forgot it's tuning limits, and let me tune long-wave below 150 kHz, all the way to zero on the dial. Whether this was any use or not, I don't know, but it was cool at the time.