My buddy is having some issues with his car. He has a 2003 MUstang GT.....fuel pump cycle will not exeed 50% and fuel pressure after 5000rpm begins decreasing to 27-30psi. The car will hold at 39-41 psi until about 5000 rpm. What could be the problem? When we data logged his car we also noticed his battery voltage dcreased from 13.7 volts down to 12.7 volts near redline? What could be happing...could this affect the duty cycle or fuel pressure?? He is running a boost a pump and a focus fuel pump. Please help.