Q: what damage can an improper tow do to a front wheel drive automatic?

The landord of the complex I work in, towed my car to plow. I found it a half a football field away from where I legally parked it. I found punctures in the undercarraige and it was running rough. After taking it to the dealer, I asked them to check everything out, but they only drove it and said they diagnosed it, but found nothing. A week later the check engine light comes on and they said it needed a system update? Couldn't diagnostics tell them that the previous week? Well, now my car is getting even worse. Upon ignition (warm weather and even warm engine) it will rev to 2500RPMs jump up to 3500RPMs then after 20-30 seconds, calm down and idle at 1500RPMs. It is also using gas EXTREMELY fast and it is peddle to the metal to get it to accelerate, with loud reving accompanying it......all to just get up to 35MPH. Dealer says they can only work on what trips a code...does throttle body trip a code? Can towing cause this damage?

My car has 46300 miles.
My car has an automatic transmission.