Here is a better source of lap records for the various track configurations at UMC. Unfortunately it doesn't tell you the make and model of car in the NASA classes.
https://docs.google.com/spreadsheets/d/1GsONhXO4OCIaT0Q4ecpQk3v4pVk6-_J2vR5fvb86EDQ/edit#gid=165366706[
Mark's record is from last years PCA club race and he was the only Spec Boxster. Other specs have run in GT4 past years. One big thing missing from the ClubRace site is what configuration was run for the time.
I have TTC records in my base Boxster from when the class existed. Adam Heller's GTS2 times are from an S racecar, as are Bill Noblitt's PTB times.