Needing Help/Advice

Hi all! I have had my RX-8 for 9 years now and for the last year and a half it has not been working. I got the car right after high school without really doing any research on the engine and such. It was a great car but in 2013 I started having engine problems. So still under warranty I was able to get a new engine. Great so it was fine for the next couple of years. I was changing the oil and checking it. Driving down the interstate one night on the way home and I was trying to push the gas down and nothing was happening. I had to pull off on the shoulder and then it just died. I could not crank the engine again. So got it towed to the first shop which was Pepboys. Which of course they didn't know much about the engine so they couldn't help me. So I had it towed to the "Mazda" dealership. I say it like that because it was a dealership mostly for Ford and had a Mazda side. So they said that the coils, spark plug and wires were possibly what was wrong but they were not certain. Well unfortunately I don't have money like that for them to just guess being a college student. So I had it towed to my house and my husband and I replaced the coils, spark plugs and wire ourself because we found the parts cheaper and why not our labor is free! SO it still does not work :(. It will crank but it idles very high and then when you try to give it gas it does the same as it did the night when it quit you will push the gas and nothing happens and then like after 10 seconds of holding down the gas peddle it catches and it moves super slow. So just wondering what it could be. I would like to get it working to sell it or really even drive it again because it is completely paid off and the car I am driving now does not :( So any help would be great!

THanks in Advance
Em

Needing Help/Advice