a compression test might help find the issue...

 

so here's the results...#1 the freeze plug blew out of the stock water pump which supposedly is pretty common in evo's. So I got one that replaced it and fixed that problem. #2 a couple of the spark plugs were mis firing causing the backfiring...so all in all not too bad

 

This same thing happened to me yesterday! (happened when the car had the original pump in it as well!)

What size plug did you put in it?

 

Got one, it was a 35mm cupped freeze plug. $0.70 :P

 

There was a TSB for 2005 Evos and freeze plugs.

Glad to hear it was a simple fix.