Hacking Injecting a PAL NES game using NSUI

[SaddQ]

I have injected the PAL-only version of Rainbow Islands by Ocean using the New Super Ultimate Injector, but the game runs too fast compared to what it should.
Is there any way to slow it down to its original PAL speed? There is no NTSC version of the Ocean game, so I'm looking to inject specifically the PAL one.