I believe that was due to fan feedback concerning the first time KARR appeared, since KARR had the three-bar modulator.
I suppose it's possible, but it seems unlikely that feedback from Knight Rider fans in 1982 or 1983 persuaded producers to change KITT's squawk box. Whether or not fans snail-mailed such opinions, it seems more likely that Robert Foster just thought the three-bar design looked more interesting.
Actually, they had wanted to start the show with the 3-bar system but it wasn't working properly (or they couldn't integrate it into the car, I forget the real excuse).
When they finally got a prototype working, they used it in episode 109 as KARR as a test to see if it was effective. It proved popular with the fans, and thus in episode 113 KITT suddeny had a facelift.
I'm sure they'll give KITT three new modes in order to compensate -- Segway, golf cart and pogo stick.
You forgot ice cream truck, javlin and skate board.