Tip: If you give a Muncher tile custom graphics, it will still act like a coin when a silver P-switch is active, whether it looks like a coin or not. So make sure to use ExAnimation if there's a silver P-switch in the area.
Code that handles what overworld tiles don't play a SFX when stepped on. The tile numbers are used in 16-bit.
$04968D - Change [AD C1] to [80 10] to make overworld star/pipe tiles play the "beep" sound when stepped on.
$0496A0 - Sound effect that plays when Mario steps on a level tile. Change to 00 to disable.