98 GMC Stalling at freeway speeds

My 1998 GMC sierra has started loosing power at freeway speeds the engin dies the dash lights get bright. After a few seconds it will return to normal with full power. The dealer in my town can't seem to find the problem. Can any one HELP. When it looses its power the air bag light flashes and some time it quites with a sudden jurk.it feels like i have hit somthing on the road

I am going to ask a simple question so please take no offense. When my 85 did this at the most irritating times it turned out to be the fuel filter, and when I first replaced it the replacement had a partial blockage in it as well. I replaced it as well and have had no further problem. So have you changed your filter lately?

I am going to ask a simple question so please take no offense. When my 85 did this at the most irritating times it turned out to be the fuel filter, and when I first replaced it the replacement had a partial blockage in it as well. I replaced it as well and have had no further problem. So have you changed your filter lately?

Yes. The dealer has changed the ignition switch two times.they say it is electrical.
Thank you
REaston