Is there any way to tune a Z24 to be ran in mountain conditions? I currently reside in Colorado, but came to Ohio to visit family, and noticed a 20 to 30 horsepower increase just from the oxygen level change at the lower altitude. I have a aftermarket cold air intake (already installed), and a 52mm throttle body on the way, but is there anything else I can do to make my car run in the mountains like it does down here?

Basically..withough installing performance parts....no.

You could try disconnection your battery when you get home overnight wich should make your car re-learn its fuel and ignition curves for your enviroment a little better but it's a long shot.

My car does the same thing where I live in Minnesota. The car has a bit more power in the winter as apposed to the summer. I wish my car ran like it was 40 degrees outside all the time. You could re-tune your stock ECU with HP-tuners and that would help a bit, other than that, your kinda at the whim of your enviroment.