The Supra's rev limiter engages at redline. So 6,500RPM if you've got a 6M crank (86.5 through part of 89) or 6,250 if you have a 7M crank. There's no way of adjusting it without affecting the entire system's clock (see: everything else will be off). You may do what you did with your other vehicle and install an add-on for ignition control, but I don't think it's worth it as redline is pretty close to your target.
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.
If you're so inclined I'm always more than happy to accept tips via PayPal. 
Tip Jar ---> 
|