2004 9-5 low boost

Turbo gauge won’t go into yellow, now it’s starting to stutter and almost die out. Oil light comes on when it almost dies. Started with the P1105 code, now getting random miss fire codes. Turbo makes a hissing sound. Tried changing MAF sensor, pressure sensor on inlet air tube, valve on inlet air tube and multiple vacuum lines. Waste gate is moving fine. Also tried disconnecting the cat, didn’t seem to change just ran rough, probably due to o2 sensors. Reading other posts saying plugged cat, just want to be sure before spending the money on a new cat. So any other suggestions? Thanks

Well I found where the hiss was coming from. Blown inlet gasket, hoping that is the reason for low boost.

Would you happen to have any pics I seem to have the same low boost as you also today for some reason I hit about 110 on the highway and I got this VIOLIENT vibration I stopped accelerating and it stopped got off the highway jumped back on and trans just slipped completely had to pull over and restart to make it home

I have the 2.3 liter and the turbo inlet is on the bottom of the exhaust manifold. This is right in front of the motor as you look down.