While I am driving the power will just fade

2000 4x4 Blazer 170,000 for the past few months I would have to let the truck warm up before driving or it would take off slowly. Today I was driving into town and all of a sudden I could put my foot down on the gas but it was not going anywhere. The engine was still running, the rpms where still showing but no power. When I put my foot all the way onto the gas it started to make a pop sound under the hood or like a back fire sound. I was able to drive home after the truck sat for a bit but very worried about going to town again for this to happen.