Loss power

My 96 suburban has lost power. I have checked the compression and its is at 150 except 4 and 5 at 120. It sucks air in though the valve cover. Any ideas except rebuildingg engine

Post the engines manifold vacuum readings,unless you are done with diagnostics and are sure the engines loss of power is related to a mechanical condition,do you feel the “sucks through valve cover” is a sympton of a worn engine condition? Are you looking for a way to raise the compression on those two low cylinders?How low is the power?