There are several things that will cause that. Of a long list, the last item on it would be the computer.
However, the aftermarket chip does move it up the list slightly. It depends on the chip. Some of them are great and will make the truck run better than factory, or will correct problems caused by modifications to the engine.
Others are snake oil.
If it ever ran OK with the chip, then odds are it and the computer are OK.
You say no codes. How did you check?
If the check engine light is not on, are you sure it works? The bulb should light up when you first turn it on.
Even so, you should do a code check.
Of the several causes, probably the most likely is the throttle position sensor. That is what tells the computer that you are accelerating so it can pump in more fuel.
Which brings up the close second cause, fuel pressure or flow.
You could have problems with the fuel regulator or a stopped up filter. Or even a pump problem.
I would get a cheap ohmmeter and check the throttle position sensor first. The needle types do a better job than the digital ones.
I don't have the at rest readings handy, but someone here will know them. The main thing other than that is a nice smooth movement of the needle as you move the throttle.
After fuel, the next thing is the EGR system.
