We think the reason our PING sensor anti collision system isn't working at the moment is because not enough current is being sourced to the sensors while the motors are running (they are all powered by one 9V battery). To remedy this, we're going to try one of Bill's LiPo batteries, capable of sourcing several Amps at 11V. We've cut the duty cycle of the DC PWM in anticipation of crazy immense current.
From Wikipedia: "Li-poly batteries are also gaining favor in the world of radio-controlled aircraft as well as radio-controlled cars, where the advantages of both lower weight and greatly increased run times can be sufficient justification for the price."
We hope this works.
After replacing the 9V batteries with the LiPo, every component of our system worked. Despite this, our RAC Mustang still did not run flawlessly because there were some loose connections between components. We soldered what we could (like the light system and PING) but the majority of the connections were to the microcontrollers and we weren't allowed to solder those. In the end, our car works perfectly roughly 2/3 of the time and is passable for the other 1/3.