I have a 99.5 super duty 7.3 PSD with 88,000 miles on it. for the last 2 weeks it has been hard to start. changed oil, oil filter, air filter, and fuel filter 2 months ago. HPOP is full of oil don't see any leaks on HPOP oil lines. scanned truck and it is showing codes "P1670 EF Feedback Signal...