Need Tippmann C3 Technical Info

Not sure if this is the correct area to post this question, but I couldn't find a better, so here goes.  I hae read the specs on the C3 and was wondering how much of an effect will altitude be on this gun.  A typical altitude I play at is 8000 - 10000ft.  I understand the small gas engine mechanics, so Im wondering what would be the max velocity of the gun at these high altitudes compared to sea level?

From my understanding, when you go up in altitude you have less oxygen to burn, thus you thin the fuel mixture so that you still have a complete burn and are not wasting fuel.  When this is the case you are using less fuel but are not producing the same amount of pressure.  The question would be, in this gun what is the limiting factor, fuel or air?