When Desi starts the old sports car for the first time, the license plate is a European Union plate beginning with "6PG". 6 seconds later the plate is different, dirtier, and begins with "ROMA".
While Desi & Mac are towing the sports car the license plate reads "ROMA834N7". When Desi starts the old sports car for the first time, the license plate is clean and reads "6PG 831B7". 6 seconds later the plate is different, dirtier, and begins with "ROMA". After the car breaks down and Mac push-starts the car, the rear license plate again reads "6PG 831B7".