The subroutine that handles the score when you get a Yoshi coin.
Changing $00F37A [EE 20 14] to [EA EA EA] will stop the Yoshi Coin counter from increasing and giving you points and giving you a life after you collected enough for one.
Subroutine to spawn a score sprite at Mario's position. Load the score sprite to spawn in A before calling; alternatively, jump a few bytes earlier to $00F388 to specifically spawn a 1up score sprite.