So I got it in, started on the first crank. Took it to the lake and it started right up, good oil pressure. Didn't sound quite right. Before I could run it much more it stalled and wouldn't restart. Backfired, blew the muffler off the flanges. Pulled it out and took it home. Pulled the plugs and only 4 indicated burning fuel. Then I put new plugs in and it definitely isn't firing on all 8. Starts but running rough. Checked all the connections. Guess I need a MEFI 5 scanner tool to see if it is throwing codes. Any other suggestions while I try to find a scanner.

Bad coil packs? They are brand new I believe.

Just grasping at straws.