There is a different approach to make the NSX to perform more equal to the other cars. This has been tested also in racing with very good and experienced drivers and it works. Again, its different and you guys might not like it, but be open minded when you read below.
The root problem is that the NSX is a difficult car to drive fast and well. Its faster down the straight but has less grip in the corners. The lower in performance (HP) you go more equal it becomes but when going very low down the performance scale, the GTR/Lexus becomes boring to drive.
So the concept is to use PPs as the performance equalizer and to put it at a level where to get the best lap times in a GTR/Lexus you're running far from max downforce. In summary what happens is that the NSX becomes easier to drive than today and the other cars actually more difficult as you're not using full downforce.
To put more details on it, at 600PP (similar performance level as new regulations) on racing softs, the NSX and the GTR performs very similar on all tracks. The NSX will run with close to full downforce and the GTR will reduce downforce around 15-20 clicks to get best lap times. This way, both cars get very similar top speed and grip in the corners. Same approach can be applied to racing medium/hard tires, but the "equal PP level" might change. Then Lexus needs 3-5PP more to get on par.
The other interesting thing is that its open up the possibility to tune what level of downforce to have. In GT5, increased downforce doesn't effect topspeed (drag), but the way the implemented it with the PPs is that with increased downforce you have to reducde power at the same PP. Same result, just differently done.
I know this is different from how you do things today, so if you don't like it use it as food for thought. But it works very well.