6.0 low on power, intermittent rough idle

[oliverpuller]

This '03 6-speed manual is a mystery. It's been low on power ever since the dealer replaced a bad FICM (and I'm assuming it now has the junk updated FICM tune). It starts fine cold, but will idle rough once warmed up. Sitting in traffic, if you just barely touch the go pedal, the idle smooths out. Once you let out, it shakes and rattles the whole truck, most noticeably in the gear shifter.

Tested the FICM today using a multimeter and the method found on Swamps' site: 48.5 key on, 48.5 at idle.

My guess now is maybe try a FICM tuner or change the oil with a Motorcraft filter, maybe the blue spring mod.

EGR deleted, RCD tow tune, aFe CAI, no cat, otherwise stock exhaust.