I think the true reason salvie testa was killed was that Scarfo didnt like all the attention Salvie was getting. It almost implied he was the real boss. I also think the wall street journal article that talks about Testa as being the second coming bothered Scarfo and it kind of made him look bad to the guys in NYC, at least in Scarfo's eyes.
I really think that is what the killing was all about. Scarfo probably thought, " hey, im the boss, why is this young punk getting all this attention".