97 QX4 no power at low rpm's

[JNCoRacer]

Long story...scroll down for the question.

I purchased a 97 QX4 over a week ago. Before I went to pick it up the dealer said they had the valve cover gaskets replaced and just had to clear the CEL. No problem. I pick it up and before I even get to the highway the CEL comes on. I was late to pick my son up from daycare so I figured I'd check it when I got back to my side of town. One code came up...P0300 random cylinder misfire. I took it back to the dealer and told them to fix it along with a rattling heatshield. A week later they call and say its been fixxed and ready. Again before I even get to the highway the CEL comes back on. This time I turn back around and ask the dealer what he had done to it because the problem was still there. Words were exchanged and I was told to go to the shop that had done the work. The shop scans it and this time it pulls up P0174...fuel system lean bank 2. The shop cleared the code and I went on my way. Today the CEL comes back and I have both P0300 and P0174.

The question...This QX4 has no power at low rpm's until it hits around 2700rpm's and then it surges and will throw you in the back of the seat. Is there anything I can check that would be the cause of this? I'm new to the QX4 but not to Nissan. I've owned 3 4th gen Maxima's and diagnostics seemed to be easier on those.

Thanks to those that help.

Jarrod