I have a BNR stage 4 at sea level it was boosting 7psi I have since moved to 7100ft and it can only boost 5psi. I have hooked a boost guage up to the WG and it is opening at 5psi. I have not changed the WG spring any. Is my loss of boost due to the elavation or possibly something else?

 

thinner air up high, would make sense, just like cars boost higher on cold days. because the air is thicker.

 

The type of boost control you have will affect the opening of the wastegate. Many cheap, manual controllers will have significant fluctuations of boost depending on the atmospheric conditions (density mostly). That could be the issue. A good electronic boost controller should provide consistant boost pressure.

 

There is no boost controller, just the wastegate spring. If it opened at 7psi at sea level that it should still open at 7psi at 7100ft. Right?