Hello all,
It's been a while since I bought my Pacer, but sometime back then I must have noticed the same thing. However, after digging around through all the Pacer files, I noticed that the
Bush version DOES have its own sound set. Here's it's directory location:
C:\ . . . \Microsoft Flight Simulator X\SimObjects\Airplanes\Piper_Pacer_LHC_Bush\sound
I aliased the other Pacers' sounds to this location and now they all sound sweet!
You might try that and see what you think. Alternately, you could just take a spin in the Bush model and see if you like how it sounds before switching the others. I wonder if the old Maule sound reference was a "leftover" from when they were developing the model . . .
Have fun,

Michael