First of all, an EV can never draw 48A out of a NEMA 14-50, because an EV is a continuous load, and continuous loads are limited to 80% of the capacity of the circuit and outlet (so 40A). And the newest mobile connector caps out at 32A; this is a limitation of the mobile connector itself, which can't draw the full 40A the outlet is capable of supplying.
If you want 48A charging, as others have said, you'll need a wall connector or other brand of EVSE that supports 48A continuous (which requires wiring capable of supporting 60A due to the 80% rule). The wall connector or other brand of EVSE must be hardwired because there aren't any outlets that can support 60A of current. You also cannot use the same wiring you installed for the 14-50 unless you used wiring capable of supplying 60A.
Right, This OP, even if they bought a tesla wall connector or some other brand that was capable of 60amp circuit / 48 continuous, because they installed a 14-50 and it can not be run at 50amp for continuous charging, the best they will be able to get out of that for charging a car is 40amp.
Thats 8 more amps than they are getting now.
Its Highly unlikely that an additional 8amps of power will make any meaningful impact on this OPs actual usage of the vehicle. To get 48amps they are going to have to:
1. Buy a tesla wall connector or some other evse that supports 48amp charging
2. have the 14-50 removed and hard wire the evse they purchase
3. Verify that the wiring ran for the 14-50 is actually capable of 60amp instead of the 50amp it was originally installed for (probably not).
4. Remedy point 3 by having appropriate wiring re run for 60amp / 48amp continuous
5. Possibly remove GFCI breaker that should have been installed with the 14-50 for EVSE charging, and replacing it with a non GFCI breaker as the wall connector EVSE doesnt need a GFCI breaker.
Or... they can just go with what they already have installed, which is 32amp charging.
EDIT: I see they mention they ran the appropriate cabling so if thats the case, no cabling would need to be replaced.