I was driving my 05 s60R on the high way and I was at the top end of 4th gear then I hear like a psssss sound I lost almost all power the car took forever to get up in RPM and speed, I can't get enough power to spool up the turbo, anyone have any suggestions on what it could be?

 

check to make sure there's no air leaks in the turbo to intake air path - look for a hose that may have blown off or a tear in a rubber bit.