Does it ever do it at idle or while in park? Mine does and I was enlighend as to a few things I could try. Things like checking fuel moisture separator/filter. I don't have codes either but this morning I expirenced a surge while at a light and I was looking at the tach waiting for it and noticed it was at least a 250 rpm surge. It only lasts for a mili-second but feels like a vehicle bumped me from the rear. It did it twice more while at normal driving speeds. All within about 5 miles.
Let me know when you find out what your problem was, meanwhile I'll attend to the filters etc etc and let you know what the outcome turns out to be.