Starts but has no power?

I failed to say that it has a new timing belt. Another question I have was. When I pulled the spark plugs out they was soaked with oil on top an bottom of all 4 cylinders. An it has a new valve cover gasket.

Ok if you have oil inside on plugs you have bad rings or bad valve seats,it wont have power if this is the issue,you will have to replace head on engine or have it rebiult.

Thats was my answer too my friend I was doing the work for but was wanting to talk to someone that knows about Kia. I've never worked on any Kia before until now. I was thinking that could be valves, piston or rings. Thanks I appreciate the advice!