I think there's still junk in the exhaust and bottling up the engine. To test, unbolt the headers and then test run.

I once had a 76 dodge p'u and the converter plugged up and it stopped dead.. and there used to be a practical joke where you'd push a potato into the tailpipe, big enough to stop all flow.. car would start for a few seconds never to run again if the potato (and the exhaust) were sealed tight.

I had a customer from the shop who backed into a snowpile then went into a store.. when he came out his car wouldn't start.. he called me and I was lucky to hear the exhaust pipe wheezing.. I used a tire iron to poke a hole in the pipe and it started and once hot enough it blew the snow out and was fine.

So try it, it might surprise you..