I've had the SPE DPK on my 2012 6.7 PSD for only 2 weeks. At operating temp it would have Hard starts, rough starts. What appears to be Low fuel pressure before the HPFP kicks in. But no codes. So I replaced the fuel rail pressure sensor. No change. Removing the SPE Exofilter solved problem. But now the fuel supply line (upper fuel filter to the SPE DPK manifold ) supplied by SPE humms (vibrates) like mad while the truck is running. Fuel rail pressure to the injectors is fine, acceleration is fine. Just a constant humm. I'm at a loss as to how to fix it w/o removing the SPE DPK.