Fueling & Injection - Octane Availability Question

I live in Tucson, AZ and the highest octane rating we have here is 91? Is this a problem? I know many of you are using 93 and that seems to be what is recommended. Also does elevation effect the need for higher octane gas?

91 should be good for you, if you have not raised compression. If you mod it make sure you have it tuned by someone good.