Chris Bridge is wondering about compression ratios:

 An additional factor you may want to consider in selecting your compression
 ratio is the altitude where you live. If you are living several thousand
 feet above sea level (you are in AZ, right) the compression ratio you 
 mentioned may be appropriate since you are starting with less atmospheric
 pressure. You will probably need to run premium gas and listen carefully
 for pinging on trips to sea level destinations though.

 Good Luck!

 Dave