[twobjshelbys]

If you're looking to EFI to keep the power in Payson the same as in the valley that problem won't be solved with EFI. Every engine suffers power loss as altitude increases. There's nothing you can do about it until they repeal the laws of physics. (Just ask the top fuel dragster guys at the Denver Mile High Nationals.) All a MAF based EFI system does is automatically keep the Air-Fuel ratio at ideal so you don't run rich. That's why the EPA loves this type of fuel injection - it's all about emissions. But without the MAF to sense altitude (air pressure) the other calibration systems are basically static and deliver the same results as a carb.

Like spdbrk says if you are looking to make a high altitude car like a low altitude car get a supercharger. But that's static too and can be dangerous. A friend put a Paxton on his 2006 Shelby Hertz. He set it for 8lb boost in Denver. Well, the 4.6L3v maxd out at 8lb. When he took it down to sea level and ran on a track the engine all of a sudden saw 10lb boost and literally exploded (piston through the wall)... (He replaced it with an Aluminator).