I have a 2001 duramax 2500HD with 135000 miles. I swapped the injectors that the auto shop I went to told me were bad( the whole passenger side). The truck ran better than before but still when into limp mode when I put a load on the engine. The codes that it has are a P0093(had that before the swap) and a U1800. Could the problem be the cp3 pump and if so could I put a lift pump to help it?