i have a 2006 f150 with the 5.4. Anyone try and clean the intake manifold, i understand that these engines have a flaps in the intake runners. Do you think by cleaning the intake plenum that it would make the engine smoother?

 

If there is some obvious debris lodged in it then pull it out, and clean it. Since its plastic you shouldn't use any chemicals.. You may be due for a good throttle body cleaning and a MAF cleaning. You need to remove both to clean them. Use only throttle body cleaner on the TB, and MAF cleaner on the MAF. Follow this up with a seafoam treatment and your motor should be purring like a kitten.

Seafoam and mopar combustion chamber cleaner are both great induction system cleaning products..