BAckground.
I have a 2004 F350 with almost 120k miles.
The truck is definitely not as powerful as it used to be especially when towing, and espically at lower RPMS. Most of my driving is short distances (<5 miles) with occasional highway
I have routinely changed the oil and oil fuel air filters.
I changed the plugs several years ago at about 90k miles when I had a coil pak fail.


What are some things I can do to clean up the engine inside and hopefully restore power?
Heavy dose of fuel additive?
Seafoam or other into air intake or vacuum?
Something to put into the oil to clean that side of things?


Thanks!

 

You probably have some residual sludge build-up within the engine. Those 5.4L are good and bad at the same time but they are built to last a long long time if you treat them well. Use a motor flush, change out the oil, and use Risolone additive to your motor oil. That should help clean up the inside of your engine restore some lost power.

Also the installation of an air intake might be the next step. The 5.4L were notorious for not getting enough air supply, if you really want to go that far - Other than that it just gets expensive and time consuming. I'd just run her for another 170K miles.