as for the sticking tappet, you got the right grade oil in it? you MUST run the right oil in zetecs otherwise they do this.

as for the missfire, you taken off leads to see if its one particular cylinder thats not firing? could be coilpack, in which case itll be running on two. could be a dodgey injector plug/blocked injector. could be the airflow meter, either the plugs come off or theres a big airleak, hose come off or something, ive had this before.

could be lots of things mate, start checking stuff one by one.