I don't think that it will hurt the injectors, gas is gas. The o2 sensor might be a different story with the leaded gas. You could always use some e85 and that will clean out the injector for sure. E85 is cheaper too.

 

All leaded fuel is dirty.....on the exhaust side..... Like I said nearly all of the import racers in my area have been using it for many years. For the $90 a new O2 sensor cost I don't really worry if I have to replace one every two years. That being said I never have had to.

 

You should not have any problem with your injectors, I use some good injector cleaner in a full tank every six months running 100/110 mix (110 leaded). O2 sensor like everyone else said should in theory go faster but no one that I know have had one go yet because of running race fuel on the evo. If you have a cat, leaded fuel will clog it up pretty quick( a year of constant use I guess). If you are running 104 only when you go to the track I would not even worry about all that stuff.