Hello again, Opti trouble once more. Last 2 days my car died on the highway while driving in 6th gear, low RPM's . There is a miss, then the tach needle falls to the bottom. I call for help, then about 5 minutes later it restarts. Fires all the time for my mechanic and the next day same situation repeated.

Short of driving with diagnostic tool plugged in, any insights as to what is causing this?

This is my 5th Opti and first non GM one {Summit} thanks for reading.