1997 Cavalier has no power
I just bought a 1997 Cavalier 2.2 manual transmission off my buddy. It started running very badly about a month ago and I got it very cheap. The cars starts and does not stall, is not smoking or leaking anything but it has no power at all. It will not go above 30 mph and will not climb hills at all. Previous owner cut the cat off and replaced the plugs. I replaced/checked the plugs (checked for spark and compression tested) coilpacks, ignition control module, wires and visually checked for vacuum leaks. It is throwing an O2 sensor code and multiple cylinder misfire. My mechanic wants to pull the head and go from there but I would like to explore other (cheaper) options first. The CEL is the only light on. If I have to replace the motor I will but what am I missing here that I can also check? I have read to have the fuel pressure checked??
I thank you in advance for any advice. Thank you.