Mark,
Chip or Tongue mufflers available for the LA25 are lighter than the stock OS muffler by an ounce and more. They are a bit louder, but don't seem to cost power. In fact, on an LA25, I've seen a gain in RPM, same steady low-2 run and economy on an APC 9-4; 10-10-10 fuel. Not all chips are muffler tapped, but that is not hard to change.
I fly at 5,000' usually, or at 2,400' occasionally, and the above has been consistent at both.
Your model is small enough that trimming an ounce-plus off the front end might be worth considering...