Here check on some of these issues for your help on your problems, good luck and let us know what you find out.
Pontiac Bonneville Starting/Stallling/Ignition Issues - CarSpace Automotive Forums
Its a great little problem solver site from people who have had troubles with Bonnie'*
My problem was a bad crank sensor and a bad O2 sensor I have had them for over a week now and have had no problems yet. My car would just die while I was doing 70 down the highway yikes or just doing 35 around town. The new sensors so far have solved my problem. I got A1 help from all of the fine folks here and I want to thank them all once again for helping me get my Bonnie back up to speed! Only a little more work to go and she will be all done........