See attached diagram.

 

did the problem make the gauge light / check engine etc .. light come on on the dash?. I have a friend whos V6 is playing up, rough starts, runs with low power. I suggested relacing everything you have but didnt think about the cam / crank sensors. Ill let them know, cause we are in the UK scanners can be a problem so we have no codes, thats why i suggested the old school spark plugs, wire, filters, o2 sensor etc.