This is the raw laptime video you've been waiting for.

Both cars are bone stock:
1990 BMW M3 E30 (USA-specification), 2861 lb
1985 Mercedes 190E 2.3-16 (European specification), 2845 lb

Both cars are wearing brand-new Vredestein Sprint + tires in their original size, 205/55-15

Laps conducted back-to-back, same day, both driven by SCCA Hall of Fame driver Randy Pobst.

The E30's front shocks blew on track; the W201's ABS failed en route to the track. Such is the life of old cars. All else being even, Randy's prediction is that the cars would have been within a few tenths if both issues were fixed. 

Full video: https://www.youtube.com/watch?v=u3EiY7sQWr4

RANDY POBST LAP TIMES at THUNDERHILL WEST (2-MILE)

1:21.51 2021 BMW M4 6-speed (G82)
1:22.12 2021 BMW M3 Competition (G80)
1:23.82 2017 Porsche 911 Carrera (991.2)
1:23.87 2016 BMW M3 Competition (F80)
1:23.89 2017 Alfa Romeo Giulia Quadrifoglio
1:25.38 2016 BMW M2
1:27.03 2006 BMW M3 ZCP (E46)
1:34.59 1985 Mercedes 190E 2.3-16
1:35.34 1990 BMW M3 (E30) 
1:40.85 2021 Kia Telluride