Nokia CARK126 and 6100 / 6820

Hi Guys.

i have recently upgraded my car kit to a cark126 from a cark91 and
have the following simple question

since i have installed the kit, using my 6100 at full volume produces
an unacceptable level fo distortion and clipping as if the speaker
cannot handle the input! this is similar on the 6820 but not as
promounced.

i have tried one other phone a 6100 again and this was the same.

i wanted to know if anyone else had this problem before i start
complaining to Nokia as it could be something i have to live with.
could it be software on the handset?

i look forward to your replies and thanks in advance for your help.

regards

Kerry Burn