I very rarely view boost thru my scan gauge, but yesterday morning I started the truck and it was reading -3.x psi boost at idle. My Isspro boost gauge is reading correctly. Both go up and down with normal driving like usual, just the scan gauge reading starts out as a negative number. I am assuming the scan gauge gets its info from the map sensor. Is this an indication my map sensor is going bad? Never heard of these things going bad.