On an earlier post of mine, I asked a question and come to find out, the problem seems more than anything to be the Knock Sensor. My question now is where exactly is this sensor located and how hard is it to remove/replace. The engine is the 4.6 but Im sure its the same between the 4.6 and 5.4.

 

Look in the center of the block under the intake manifold. That's where mine was located. Some engines have 2 knock sensors but that is the only one I found on mine.

 

X2, it's under the intake manifold in the valley.

 

Smack dab in the middle. You will have to remove the intake to change it. At least the intake gaskets are reusable or reasonably priced if you want to put in new.