When using sunshin combined with his max speed he is already as fast as Minato USING FTG, because only when using FTG he became yellow flash.
Naruto on sheer speed is already as fast as Minato using FTG, he just needs to be able to use it on a consistent basis rather than being an occasional speed and he will have even surpassed FTG because Naruto doesnt require seals to do it.
FTG is instant teleportation, not movement, which mean that even if he combined FTG with his speed it would be irrelevant. Naruto learning it would be irrelevant, it would improve nothing.
Naruto on sheer speed is already as fast as Minato using FTG, he just needs to be able to use it on a consistent basis rather than being an occasional speed and he will have even surpassed FTG because Naruto doesnt require seals to do it.
FTG is instant teleportation, not movement, which mean that even if he combined FTG with his speed it would be irrelevant. Naruto learning it would be irrelevant, it would improve nothing.