I think what I thought was a problem has turned out not really to be a problem. When I am connected to my car BT and I press the Home button on the iPhone, the Siri bing would start but my phone, through the BT connection would start dialing home. Well, I thought it was dialing home, but what it was really doing was connection to my iPhone cell phone number and when I looked at the car display screen quickly, it had looked like it was dialing home (it showed my name and then the time start counting which is what it does when it is on a call.)
When I looked closer, I saw it was displaying the time counter on the car screen and my iPhone's cell phone number. I guess in order to route Siri and voice commands through my car BT head unit, it sort of treated it as if it was calling itself and showed how long the connection was open.
Anyways, I am not sure this makes sense or is clear, but to make a short story long, it now seems to be working fine. I can connect to my BT headunit in the car, make calls and answer the phone the way I always used to, and if I need to access Siri while driving (either to read to me or reply to a text that arrived while driving) I can do that all over the car speakers.
Thanx for the help.