The generic MAF PID will max out at 655 g/s. Try logging enhanced parameter AIRPERSEC instead.
The generic VSS PID will max out at 255km/h (158mph). Try logging custom parameter VSS_M instead.
For future reference you can search all PIDs for a specific type of unit. For example if you want to find any other PIDs that return grams/second, just search for g/s, like this:
The search will also find PIDs that have matching names and/or descriptions (not just units) with your search criteria.
Regards
Paul