It was more of a a very harsh "bark, bark, bark" loud enough you could hear it in the air filter. Could be some other issues there also that I haven't found yet.
The head is coming off regardless now. Valves leaking that bad can't be good. New guides, new valves?, probably O-ring it too. Drill the divider on the HX-35 exhaust housing while its off.

 

I had the same thing happen to me. I cut each cylinder out and had the same prob. Didnt know what to do. put on different ecm still same prob. different injectors and pump. still prob. Ended up being connector tube between the line and injector. Oh well live and learn.