I have a '95 mustang gt and replaced the fuel pump not long ago with a bbk 155LPH. All of a sudden the car feels like it's loading up with fuel, because it is sputtering in drive going down the road at low rpm and tripping check engine lights. It runs fine at WOT, but I noticed when I turn the fuel pressure down, it gets alot worse. It started a few months after the install. I scanned my stang and code #543 came up. The code is: Fuel Pump Secondary Circuit Open PCM to Battery. What is this, and how do I fix it? Thanks