Chev Tahoe

I have a 1998 Chev Tahoe with a 5.7 Vortec. I just replaced the engine with a rebuilt long block that did include oil pan with new oil pump. I did use the upper and lower intake from my old engine. With the new engine I did put on new spark plugs, plug wires, thermostat and fuel regulator. I am now getting engine codes of P0171 and P0141. I have done the following trying to fix it. I took it back to the shop to check for intake and exhaust leaks, replaced all four O2 sensors, tested the fuel pressure, changed the MAF sensor and PCV with one of my other vehicles, cleaned the air filter(i have been using the K&N style). I engine seems to run fine with good acceleration and now visable signs of problems.
The old engine had 270,000 miles and I had continued trouble with misfires on number 4 cyclinder. I suspected cracked head or block and it was leaking anti freeze into that cyclinder. It had b