Last night during dinner a buddy of mine are talking/planing to go to Havasu & Lake Mead this spring/summer. I brought up question as to if my motor was going to run leaner or richer in the different areas. Houston is hot & humid. Havasu is hot & dry. I know the higher elevation the leaner you jet. I thought that since more water in the air there was less oxygen, so less fuel but buddy say need to richen up. Last question, will it make a big difference if I do nothing.

Motor is 540, procharged with stage 4, Do not know what HP will be yet. Just putting motor together.

Generally as a rule of thumb the higher the elevation the less jet in your carb. An easy way to think of it is to relate it to yourself. When it's hot & muggy out you can't really move without loosing your breath, and breaking out sweating, you need more air (less jet) when it's cool out you can breath real easy (more jet)