2006 F250 6.0 King Ranch - Just bought a month ago w/150K miles.
At freeways speed, around 1500 rpm, I get a shake or shimmy until I can get a few more RPMs. It only does this when I am maintaining speed (55-60ish) or going on a slight incline and I am accelerating SLIGHTLY. Today I was trying to pinpoint when and what was going on, I noticed that the RPM gauge would sit on 1500 as it shook and occasionally jump up smoothly a few RPMs and then back down to 1500. Other than that, it runs great. For the life of me, I cannot figure out what is wrong. No codes. I've thought about stiction, but does this no matter how warm it is. I've also thought about a sticky accelerator or a bad FICM. Can someone give me some ideas?

Background - performed EGR delete about 3 weeks ago and broke 2 injector connectors. Over the last 3 weeks, I've replaced all the injectors AND the wiring harness. Had noticeable miss for 2 weeks because wire broke in harness that I didn't find out about until after replacing injectors.

 

Sounds like injectors to me. Do you have a scan tool or anything like that? I'd do a power balance and make sure the motor is running right. It's not uncommon to get bad aftermarket injectors. Did u use ford remans? Also check icp voltage. I've had several part where there was no issues with the icp until I screwed with the motor. I've had guys come in for driveline issues lots and it turned out to be a sticky injector. If they arent torqued properly or the clips aren't perfect it will run funny like that.