We shouldn't let a fear of someone enjoying a benefit we feel they don't deserve get in the way of improving noise levels for others.
The high/low tax I propose isn't about preventing the worst offenders: it's about pulling the overall fleet noise levels down. The noise pollution we suffer from isn't exclusively from a few infernal racket makers -- other measures (like the articles cameras) are needed for nuisance cars.
Even if you're only concerned about the worst of the worst, lowering the average levels should make it easier to act against the worst of the worse through lower limits and harsher penalties because they'll be more separated from ordinary vehicles.