I posted to Facebook and got lots of discussion about the FM bandstop filter.
When I started adding better external antennas, I could reach further (tx and rx**, but I also found that some VHF frequencies got much worse. It turned out I was overloading the receiver with the strong FM broadcasts in my area and increased sensitivity of the better antenna. I found a bandstop filter helped bring back those signals I was losing.
Update (2024-07-17): It turns out, the noise I heard interfering most with the Monday Night 985 Workbench Net was another net on a repeater in the opposite direction and 15khz off the 985 frequency. That signal started up at the same time as the 985 net and overwhelmed my radios. The filter helped a little, but not really, it seems. I eventually resorted to a directional antenna for real improvement. I’m fortunate the repeaters are in opposite directions.