'93 Miata gets cranks but won't start! Please help!

[nicdotson]

My buddie bought a '93 Miata and drove it for two or three days and had to stop because he didn't have a tag for it yet. We replaced the steering wheel, took out the airbag, and tore the horn wires out. He went to drive it about 2 weeks later and it felt as if the alternator was going out (rough idle, just felt groggy) and quit running. Charged the battery and nothing. Charged the battery more and he accidentally stuck it in the backwards. We thought that fried the alternator and replaced it, it started and ran for about 10 seconds and back to how it was. He has replaced the camshaft position sensor, the ecu, the main fuse twice, the spark plugs, the plugs and wires, the coil pack, and the igniter. Still nothing. Hooked the horn wires back up how they were and tested the battery and alternator. They were fine and still nothing. We read that it could be the air bag module (blue box under dash) it was fine and still didn't work so we left it out. The check engine light doesn't come on when the key is in the on position so the ecu isn't getting power. It's getting fuel and it will crank but no spark and won't turn over. Its been to two different shops and they're still not sure what's wrong with it. Any help or advice would be great! Thanks!