Got Shell 93 Octane and now barely idles 1973 Dart 340

If you think it is water in the gas, Heet is a cheap fix that may help you out as long as there is more gas then there is water in your tank. I put it in and let it sit over night, it mixes with the gas and absorbs the water.
8 gallons of the previous tank was good and I filled up of 8 gallons that could possibly be "contaminated"