Van shudders

Hey guys been here alot lately, my 1995 TranSport,3.8 has shuddered alot for awhile, thought it was tires but it is not. When you get up to around 65 or 70 MPH it feels like it is stopping then restarting on its own real fast over and over, could that be fuel related,need help. HELP

What is your engine RPM at that speed?