Hey guys, if this gets a little long winded I apologize now. Here's the deal, replaced my 4.6 Romeo block with a remanufactured Windsor block, believed to be out of an explorer don't know the year, npi heads and reused the stock intake, egr, etc., well now it keeps throwing a P1406 code ( differential pressure feedback downstream hose off or plugged ). I have verified that the hose and mounting tube are clear of obstruction, by 1) attaching a vacuum pump and 2) attaching a vacuum coupling and another piece of hose and did the old suck/blow bit and had flow both ways. I'm thinking that the dpf sensor ( otherwise known as the egr position sensor ), is bad. My reasoning: the egr valve or solenoid can't be bad or I would be getting codes for flow malfunction, insufficient flow or egr regulator circuit ( solenoid ). Also the orifice in the tube assembly can't be obstructed or I'd be pulling codes for no flow or orifice restricted. The car passed the NJ smog nazi emissions test while throwing this code. and tripped the mil while they were doing the dyno test. Is there a difference in the location of the orifice tube assembly in the windsor as opposed the the romeo and are my suspicions on track, you guys probably have a whole lot more experience with these things than I do. Thanks, any input greatly appreciated.