Chip mods at high altitude

["Doug O'Neill" <doneill@skyconnect.com>]

I've been considering chipping my 97 A4 1.8Q, so I've been following the   
chip threads posted here.  However, I still have a few reservations.

I live in Boulder, CO.  Will the chip mods have the same effect at 5600'   
above sea level?  Most hop-up shops claim 40-60hp gains using their   
chips; what percentage of those gains am I likely to actually see?

Additionally, would I still be able to pass emissions tests with the new   
chip?

Thanks,
Dougo