I purchased a Kyosho Inferno MP 7.5 about 3 months ago. I broke it in outside when the temperature was about 45 degrees. Now I'm going to run it again because it's finally warmed up. So say the temperature is 70 degrees now. Does anyone know if that will affect my needle settings and if so how will it affect them......leaner?.......richer?

you will probably need to lean the HSN

Well I didn't know.....because I'd always heard that when it's warmer the air is thicker thus having more oxygen. More o2+more fuel=more horsepower?. Is this not right?

You have it backwards

think Cold Air Intake cold air has more O2 more O2 needs more fuel

Now the temp is warm so you are probably running rich.

nitro engines are also affected by humidity too!
the colder denser air will need more fuel to get the correct mixture, but then the engine will need to generate a bit more heat to get up to temperature!
you just gotta tune em on the morning when you go out & then any minor adjustments as needed during the day to keep them running sweet

The tune on our little glow engines is more effected by barometric pressure than ambient temperature. However, these two factors are usually closely related. Hotter weather is commonly associated with clear skies that are produced by high pressure. The high pressure means there is more oxygen available so you need to richen the high speed needle so the air fuel mixture is balanced.

Low barometric pressure is usually associated with cloudy or foggy weather that is accompanied by higher humidity. High humidity means there is more water vapor in the air. The air may seem thicker but the water vapor that makes it seen thick is actually displacing the air we need to ignite the fuel. So in thick moist air there is actually less air available. Less air means you have to lean out the carb so the air fuel mixture is balanced.