I have a 99 SD installed Superchips Flashpaq 1855, performance tune after a week checked codes got P1247 Turbo boost low. I then returned to stock drove for a week no code tuned performance again drove normal no codes and the first time I got into I get this code. What would cause this and any ideas what to check.

 

I had the same code pop up on mine. For me it ended up being the map sensor hose came off.