it almost sounds like the high-speed idle isnt kicking down at all. I had a similar problem with my truck (when it was running
) but that was because the new carburetor wasnt set properly. You dont have a carb to adjust, so Im not sure what would help. Before you do kick down, what does the engine sound like? If you have a tachometer, what rpm does it show before and after? Is the engine warm/cold when this happens or is it anytime it's on? Go down to a parts store (Autozone, Advance...) and have them pull the DTC's and copy them down then repost them here. I suspect a timing issue, or a confused computer.
hope I can help.