I know I probably say this a lot, but there are many cars in GT4 which handle beautifully just as they are, and this is one of them. Use the RR weight balance of the car in combination with throttle control to tweak the over / under steer of this beautifully balanced machine instead of messing it up changing it. It is like a dance, and yes, it takes time to learn, but once you've got it, you'll never look back.
Or, if you don't mind changing the handling a lot, and want it to handle more like the Yellowbird, for more of a drifting experience, use 1 grade harder tire on the rear than you have on the front. I keep one of these that way because it is truly a blast to drive with R1s on the back and R2s on the front!
Sure, there are also plenty that handle like complete crap, and those might deserve whatever you do to them to make them handle better, but for great cars like this one, why not just add some power and maybe better tires and have fun?