My 2003 Jetta won't stay running and backfires through the intake.

The car drove home after work just fine. Got up the next morning and she wouldn't start. Replaced coil pack about 500 miles ago. Pulled plugs and they were fouled bad so I replaced them. Un hooked exhaust to make sure it wasn't my catalytic converter. It will start for just a couple seconds but the whole time it's backfiring through the top end. What else should I be checking?