After struggling mightily to get my Sport to run right after the last Decent Tune-up, I tracked down a series of contributors. As is common, so many issues are "multi-causal."
I found a slightly flinky TPS and replaced it with a PF3C from cacycleworks. Spraying throttle body cleaner on the ends of the throttle plate shafts revealed a significant leak on the bottom left. I recommend this simple test for vacuum leaks when you tune-up, especially as these V11 get up in age and mileage. Check the shafts, rubber mounting boots to the intake manifolds, as well as the vacuum taps. I neglected this last step and later noticed discoloration around the left tap. Snugged up almost 1/4 turn! Also replaced the dried-out cracked rubber caps that have been on there for years.
The difference in idle stability, popping and backfiring from that leak has been an amazement!