1987 2.8L 4X4 Automatic. Purchased a month ago. Changed out the MAP sensor, added the pre-heater hose, got a new serpentine belt installed as well as changed oil and air filter. I was driving home yesterday from picking up an EGR gasket to clean the EGR valve when it started bucking when accelerating. I would go through cycles of being able to accelerate up to 40 (although rough on the way up) and then not being able to do anything over 15 and back and forth. Got it home and let it sit for two hours. Started right up, took it around the block and there was no problem.

Cleaned the EGR valve this morning, was very nasty. Thought that would fix it. Helped a little. Starting throwing code 44. Changed the O2 sensor. Way easier than I expected (took about 15 minutes from beginning to end). Tested it out, and it is much better. Thought the code was gone after leaving the negative off for about 5 minutes. Took it out for a spin, acceleration was pretty good up to 70. Twenty minutes into the drive, threw the code again. Acted a little wonky, but only did so going up a hill at 60. Anyone have any ideas about how to fix it? Could it be a vacuum hose, and how do I check? I will say that I am not the most mechanically inclined person, although I did complete the other tasks listed with the help of this site and the interweb. Thanks in advance.