I took my vehicle to a mechanic who fixed my fuel pump after my car was randomly shutting off while driving. That didn't fix the issue so then he put in a new relay. That didn't fix the issue and now he says he is going to have to install a new computer. He said it 1,000% isn't the spark plugs although I have 108,000 miles on them. How can he be certain they aren't the spark plugs? Is it because of the error code? I just don't want to throw in money when the actual problem isn't being fixed... Also after the engine stops, it doesn't turn back on right away. I have to wait like 30 seconds - 2 minutes for it to start back up otherwise it would just be cranking (I have a 2006 Mustang GT)