Q and trailer propane heating problem

I hope someone can help here. I'm at 8000 feet in the rockie mountains. I hooked my Q up to propane on are trailer. After 15 minutes it barely hit 400. Is that normal at this elevation or does elevation have anything to do with it? At home at 1000 feet it hits 500 or more easily in 10 minutes. I read somewhere that hooking up to trailer may take longer? I don't think that really makes since though. Any ideas????

Less air pressure and oxygen is going to result in lower BTU output.

Just poking around for info on google, I found a section for fire logs that claim you lose 4% of of your BTU output for each 1000 feet over 2000 feet, if that's somewhat accurate, your losing 24% of your BTU's at your current altitude.

Modern gas safety valves in propane cylinders have several safety features, one of which is designed to limit flow in the event of a hose rupture. With mine if I hook up the hose for my portable grill and whack open the tank valve I can hear the little safety valve cutting down flow- the grill gets propane but at a very slow rate. If I very slowly open the tank valve until the hose has filled then it will allow full flow once the grill is turned on.

This might be part of the problem. Or not. My Gas Go-Anywhere definitely can't sear a steak up in the mountains, but I don't think it does that well at sea level either. No matter- it does chicken, tri-tip, and burgers just fine.