2003 Ford Focus won't start

We recently bought a 2003 Ford Focus for our daughter. About 3 weeks ago the check engine light came on and it was bogging out. We had diagnostic ran and it came up p0191. Now it will not start. We replaced the fuel filter and the fuel pump is working good. We also replaced the fuel relay fuse with no luck. The car gets spark and fuel. We put fuel starter to the throttle and it popped but did not start. The car recently had a head replaced and a new timing belt put on. My husband thinks it maybe out of time but we are not certain. If anyone can give some advise it would be appreciated.