Sorry, not in California... in Northeast GA.;-)) Have you checked for computer codes by counting the check engine light pulses if there are any?
My first thought is the Vortex Mass Air Flow Meter. If this is the Karman Vortex unit you should only exchange the black electronics between the Lexus and Supra. Just requires removing three small screws after unplugging the wiring harness. If you just swap the complete units the engine is getting too much air because of the difference in design between the 6 cylinder supra and the 8 cylinder Lexus. As you increase the rpm a lean situation develops for lack of injector timing for the additional air. The computer sees a problem, as leanness will burn the cylinders and the computer restricts RPM to avoid catastrophic meltdown. By the Way.... if you do not already know. Never ever try to clean a KVAFM with cleaning fluid.. Wish I had known as it will destroy the mirror circuits by contamination. For this is what killed mine. $750.00 from the dealer. . $367. rebuilt from aftermarket. Or if one is luck can purchase used less than $100.00:-(
Larger injector can be installed to accommodate the increase airflow, but this is something for the racing or increase horse power gearheads. Hope this helps. Prof.