iPhone 3GS iOS 4.1-incoming calls on Kia Satnav-Unknown Number

Hi,
i reproduced the issue on the following hardware/software:
3 iPhone generations (3G/3GS/4)4 OS versions (3.1.3/4.0.1/4.1/4.2.1)2 Carriers (Vodafone/Orange)jailbreak/unlock do not make a difference
What happens basically is:
I pair my 3GS w/iOS4.1 to the car (Kia) Satnav -> works OKphonebook entries, caller list (missed/dialled/incoming), battery level, signal strength -> all transferred OK and visible
-When i receive a call from a number which is NOT in my iPhone contacts, the satnav displays the number but no name (expected behavior since number not paired to a name)
-If i save that number to a new contact on the phone, the next time it calls, the satnav displays unknown number! The phone displays both name/number OK.
-Similarly, if any number that exists in my phonebook calls, i get the unknown number message on the satnav. On the phone, again it shows name/number OK.
-If i check the missed call list on the satnav, i see the NAME of the contact which just called (and was shown as unknown during the call)!!!
I tried several steps with no success:
-edited my contacts on the phone to have the +XX (country code)
-tried CallerIDFix for FW 3.x but didnt notice any difference.
-restored several times to iOS4.1 fresh + set up as new phone with no contacts
-tried different language and locale settings
-saved the number in other fields instead of mobile (ex: to home or office)
-deleted all my contacts, restored as new phone: any number calls in its shown on the phone and satnav. I save the number on the phone as new contact (only contact!), give it a name....number calls again, on phone i see the name/number but on Satnav i see unknown number
-deleted and re-paired the phone with the nav several times
Ive seen quite a few variations of the same issue on these forums, but no clear indication if its a problem with the Apple PBAP implementation.
Other phones i tested work perfectly with the same Satnav:
Samsung Galaxy SNokia 6300HTC Touch 2
Dont get me wrong: the 3GS works 99% OK as well, but this incoming call issue is driving me nuts. It defeats the purpose of having handsfree in your car, since you have to check on the phone screen whos calling before answering or not.
I do NOT have problems with dropped calls, bad audio quality, unexpected un-pairing between phone and satnav, etc...
Any ideas please?
iPhone 3GS iOS 4