After digging around YouTube for Best Motoring Tsukuba battles with the Base Z34, the two videos I found of separate tests showed its best lap times to be very consistent: 1:06.669 and 1:06.754.
YouTube - Best Motoring: Seiji Ara 370Z vs keiichi tsuchiya Nismo 350Z Superleggera
YouTube - NEW 370Z vs Cayman S vs. BMW 135i vs. 997 Carrera PDK vs. S2000 Type S (HQ)
Compare that to the NISMO's 1:09:055 around Tsukuba and it comes in behind the Base by ~2.34 seconds...a
significant margin on any track, let alone one as short as Tsukuba.
For comparison purposes, the NISMO S-Tune did 1:07.110:
YouTube - Best Motoring 2009-5 Porsche 911 Carrera 4 4S Nissan 370Z Tsukuba Battle 5 Laps
NISMO fail.