My Jimmy just quits - could be at idle or driving down the freeway, can always be restarted right away and "seems" to do it less after its been running for some time. replaced fuel filter 4K ago and otherwise runs great - no check engine light either.

Any ideas?

I would check your fuel pressure first and make sure that the pressure doesn't drop. Your pressure shuld hold for a few min. after your egnition switch is off.