I just tested the compression on my engine while it was warm and cylinders 1 through 3 were at 135 psi and the 4th was at 127 psi. I've read some post saying that's ok and some saying that it is too low. I live in Utah and I don't know if that has anything to do with it since we are pretty high up and I'm assuming air pressure is slightly lower up here.

 

I believe 135 is the minimum and 28 is the max variation. Your #4 is out of (below) spec.
184 is "nominal".
Pour a teaspoon of oil in and re-test? If the values go up significantly your rings or cylinders are worn/tapered. Tapered cylinders can allow your ring gaps to open up towards the top. Oil will get between the rings and temporarily seal this.
Temperature and alt/air pressure will affect the readings very slightly.
Maybe check your valve clearances (one on #4 is too tight?), otherwise drive it while you save up for a rebuild. The Z6 is a great engine!