personally i would get the cheaper non diamond ported version and have it ported by someone here. i just picked up the non firebreather 240 and flotek as it now working his magic on it and i would feel confident lining up against a diamond racing "firebreather" all day with it once i get it back I:I I:I
You should call Ken oconnor. He will tell you how to get the best results out of porting a vito's 240. If you port the Vito's 240, talk to Ken about what exhaust to use with his porting. You will see HUGE power gains with that combination.
personally i would get the cheaper non diamond ported version and have it ported by someone here. i just picked up the non firebreather 240 and flotek as it now working his magic on it and i would feel confident lining up against a diamond racing "firebreather" all day with it once i get it back I:I I:I
There are a few tricks that need to be found when working on the Airsal that Diamond and we have worked on together. As far a the porter you mentioned. We have put their work alongside of Diamonds on the Dyno and your guy didn't fair well. Not saying that it wasn't an improvement over stock, just nothing like Diamonds work.
In my opinion, you can't do any better than Diamond, and he has the national championships to back up his work.
I personally would not buy the arisal firebreather kit. Not becasue of diamond racings hand in it or the price, the porting is super crazy and not much use anywhere but the mx, and the head is worked to run only 110 octane. I would wanna run pump.