With RB designs carb kit you have greater sensitivity on the air screw - I think stock setting is like 3/4 turns out with his mod. You need to ask what the air screw setting is for the RB design carb setup in colorado. Start out with same idle screw setting as well - (how many turns "out" and it should not be 'coil bound').
You will be able to adjust bottom end for very large altitude changes just turning air screw on RB designs carb setup.
Also - with some needles (and some that work very, very well) you run a richer pilot along with it.
jeff
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