Suggestions for muscle car sound muffler without drone

Here are the two graphs overlapped in Photoshop. The old graph is ghosted behind the new one. You can see a rise in the 2-10k range but I don't hear anything all that different in the upper range. It is an even tone now which is very clear in the graph. This was recorded on the hill that always bothers my ears coming home from work by our house.

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