I could not agree more. I am not saying "buy a turbine" but I am saying "ditch the rossi and get an OS." Beleive me, that Rossi is no bargain. While I know SOME people have had good luck with them, I have never yet seen someone put consitent flying in on one, at least not on the 90 or 105. It's no bargain, because it's almost inevitable that if you DO get it running, it WILL let you down at an inopportune moment and destroy your aircraft.
Sell it on Ebay, add a little more money, and get an OS91 or 77 and the Weston pipe. Beleive me, you will be much happier.
I don't want to get into a big "Rossis are fine if you just add an OS carb etc etc etc" debate, I just blew up a lot of Rossis and banged up a lot of planes until I got rid of all my Rossi DF motors and went to only OS. Go to any rally or local field, and count the number of guys flying Rossi DF setups. Pretty much none.
I have never seen that exact mode of failure on a pipe before, I suspect it's the wrong pipe...I HEARD about a similar failure by someone running the wrong pipe on a 105, they said the pipe melted through.
That's my two cents...I think you have an engine that is going to give you long-term troubles, I would not pursue it further, I would get rid of it.