Voltage Problem Need Help!!!!!!!!

I Have A 1989 S10 4.3l The Past 2months I Have Had My Voltage Light Come Off And On. When I Cut The Lights On It Stays On. When I Hit The Brakes It Will Go Off Or When I Hit A Bump It Will Some Times Go Off. If You Push The Brake Pedal All The Waydown It Will Go Off. I Can Kick The Pedal And It Will Go Off. And Now My Truck Is Runnig Sluggish. I Have Changed Abs Module, Battery, And Alternator. Please Any Advise Will Help!

your problem is most likely a loose ground which isn't making a good connection. Alot of times on S10's that is a problem.