Driving at higher altitudes

[Rich550]

What are the affects on the engine of driving at higher altitude and what changes in timing advance can be made to help performance at altitude?

I'm driving from the UK around the Swiss Alps in July, with altitudes of up to about 2,000 metres (over 6,500 feet).

The map I'm on currently is perfect here on regular unleaded fuel, but at altitude, would it be an advantage to have a different map that I can swap to?

Anyone any ideas?

Thanks
Rich