He is too busy using the hard earned money you father paid him to try and make his car faster. He doesn't have time to respond to customers. He got what he wanted (a pay check) so he doesn't need you any longer. Maybe it's time to take a trip down to his shop. And get what you need face to face. It's hard to ignore someone standing in front of you. Although I'm sure he will be "closed" 10 seconds before you get there and open back up 10 seconds after you leave.
