last night i was on the highway going about 70 mph. then my engine back fired and loos power. the rpm drop and rose back and forth like crazy and then shut off. started the car back up and the rpm's held like normal and would rise roughly when i press on the gas. put back in drive, would not go above 35 mph. felt like bad gas. drove home at that speed for another 10 mph. no changes upset some minor backfire...help...pleazzz!!! anyone experience the same problem....