I have a problem where if I WOT in fourth gear (sometimes other gears) I'll build boost, but then it just all goes away and it won't get anything more then 5psi for awhile then I can build boost again in other gears and peddling it a little bit. I took it to the dealer and they said it was a bad Oil Pressure Switch. I changed it out but I'm still having the same problem. At first I got a P0299 code but now I don't even get that but I still lose boost.

2010 cobalt ss