Le Sabre dies every few days

94 Le sabre v6 100,000 miles

It runs fine most of the time.
but dies on occasion.
Can find no common denominator
Examples:
Died doing 70 down ineterstate
Died doing 55
Died doing 45
Died doing 35
Died doing slowing down at red light
Died doing speeding up at red light
Died stopped at red light

What my mechanic has done so far:
replaced
cam sensor
crank sensor
fuel filter
alternator
computer
coil pack
gas cap

sometimes it will die twice in 1 day
sometimes it will go 5 or 6 days without dying

I started using high octane fuel and it seemed to die less often
going 12 days once without dying
then going 7 days without dying then finally till today going 6 days without dying

At first when it died it would start up again right away.
Later it would take a few minutess before it would start
a couple of months ago it would not restart after over an hour.
It did the same thing today.
last time It started the next day and ran fine for a few days.

What next?