I have to agree with the profiling comments. What youve described about commenting ou tthe 2d core and the music ran faster, this is bound to happen. Everything thats being used takes processing power, so cutting that processing power out will free it up for other parts to use, but it doesnt mean that code is slow, it just means its working
its like in a game on the pc, saying AA is slow cos you put it on AAx4 and your frame rate reduces, but you turn it off and it goes loads faster, its nothing to do with AA performance, its more than likely that performance is at a peak with the AA, its the fact its not being used when you turn it off.
IF it does make a difference over the official 2d core it would be good to see it run. im all for the "every little helps" frame of mind, much like saving up pennies for a rainy day :P