Boeing,
Using your approach, due to programming limitations in the sim, you cannot get the max throttle sound from any particular sound package without raising the horsepower setting in record 505 of the air file accordingly. This in turn will affect performance tremendously. The horsepower output and Engine Power Sound Level are directly connected in a simple linear algorithm that says, "raise the HP and raise the sound output".
Test it for yourself. Increase the horsepower to 4000 and note the sound difference. You'll get what appeals to your ears, but at this point you'll also be flying something resembling a prop driven rocket!
The correct approach is to edit the max throttle entries in sound.cfg. But i wouldn't recommend this unless you have some knowledge in creating and/or editing FS/CFS sound packages.
But having said all that, i did notice a disparity between the HP setting in record 500 (1030 hp) and that of record 505 (1500 hp). It may be that the sim is defaulting to the HP/sound level of record 500. Set both to 1600, which is about right for an LF Mk III model (Rolls-Royce Merlin 55M liquid-cooled V-12 - 1,585 hp). This should help you a bit. If not, then the sound.cfg is the next move.
