losing boost under load Please help
I have a 2000 f-250 7.3 has edge evolution box, mbrp exhaust and s&b cold air kit. I have noticed here lately that when under a load the truck is losing boost. I know when I first got the truck it would make 18 to 20#'s of boost before it would lose it out the waste gate. Here lately It makes 8 to 10#'s then it dumps the gate. makes a shshshshshshsh sound until you let off the pedal. Does anyone have any ideas why the truck is doing this? Any and all help will be greatly appreciated!!!!