I took my car to a second dealer and they thought it was speed sensor. They were willing to replace it under warranty. I waited for about 2 weeks for the part and turned out to be it wasn't the sensor. The problem was speedometer gear inside the tranny. At this point, they would not repair it under warranty since I have modifications. I called SOA complained and SOA approved the repair under warranty.
It's not done yet. The dealer is waiting for the part, speedometer gear this time.