All 4 cylinder misfires

I have a 2003 wrx sedan, manual trans. I read the
codes and it came back with 4 cylinder misfires, I
changed the spark plugs to see if it would solve
the issue. Before I did this the engine was a bit
shaky but settled down a bit. I erased the codes bit
still came back with the same codes. I test drove it
and gave it same gas to see how it handled it and
in the high rpm range it struggled and kind of
bogged. It gets on boost okay but I noticed after I
came back gone some light smoke almost like
vapor was coming out of the right passenger side
of the engine near the turbo. I suspected it might
of been a torn CV boot throwing grease, but the CV
boots okay. I'm thinking it might be a bad gasket
but I'm not sure. Any help would be appreciated!
Thank you.