Bojunk, code 31 is an egr code, and if the egr is screwed up, it can make the engine stall when you come up to a stop light. It shouldn't affect running down the highway too much.

griffofk, My fuel injection book says the PIP signal is the primary input for the control of the fuel pump relay. The fuel pump relay receives power from the keyswitch in the "start" position, but after the key is released, the computer must receive a PIP signal to send power to the relay to keep the pump running. The PIP signal is generated inside the dist. It's a train of pulses that are sent to the TFI module on the side of the dist, and they are also sent to the computer for fuel pump control and injector synchronization.