2001 Silverado 1500 LS 4.8L V8

Within the last few weeks my truck has beagn to buck/surge during acceleration between 45-65 mph (1500-2000 RPM). The RPMs change about 300 revs during the bucking phase. Just going over a highway overpass was enough to set it off.

OBD Codes were
P0161
P0300
P0404 before flusing EGR
P0405 after flushing EGR

This started several weeks after I replaced the
Fuel Level Sensor and
Fuel Filter (while I was in the area and in the fuel tank)

So far I've replaced the
Plugs
Ignition Wires
Throttle position sensor
cleaned the EGR (haven't received new EGR to replace as of yet)
cleaned Throttle body
cleaned MAF sensor screen.

So far the bucking has diminished in intensity and if I accelerate slowly its hardley noticeable. No OBD codes have occurred since I changed the above items.

Any ideas as to where to go next?? Fuel Pressure?

 

my mom had a ford explorer that did this after i put new plugs and wires on it turns out it needed dielectric grease on the contacts, try it out