Welcome to the forum. For future search purposes, I'm going to mention the full code definition of P0316 and P0303.
You don't mention whether or not the engine seems to be running fine or if there is a noticeable misfire. So is there a noticeable misfire? Did the parts you've already changed make any difference in the way the vehicle runs?
With the P0316 I'd be inclined to suspect the issue is more sensor related, such as the Crankshaft Position (CKP) sensor or the more likely culprit of the Camshaft Position (CMP) sensor. Usually if the CKP sensor fails on a Ford it will cause stalling and/or a no-start condition. The CMP sensor, and more specifically the CMP sensor synchronizer, have been common issues on the Taurus. Often the synchronizer will start to chirp a bit with the engine running before any driveability symptoms appear. There are several other threads and posts on this forum related to the synchronizer that you may want to search for and review.
-Rod