1997 Chevy Suburban ABS

I HAVE A 1997 CHEVY SURURBAN 2500 7.4 LITER ABOUT 129,000 MILES. MY PROBLEM IS WHEN IAM DRIVING ON FREWAY THE TRUCK ACTS LIKES ITS WANT TO STALL OUT OR LOSES POWER FOR ABOUT 30 SECONDS. THEN AFTER THAT IT SLOWLY COME BACK TO NORMAL. BUT DURING THAT TIME I NOTICE ON A FEW OCCASIONS THAT ASB LIGHT COMES ON THE DASH THEN GOES OFF. I HAVE CHECK THIS OUT ONE TIME BUT THEY DIDNT FIND ANYTHING. THIS DOES NOT HAPPEN ALL THE TIME. WHEN PULLING MY TRAILER UP HILL YOU LOSE ALL THAT POWER.