Hello all, I am looking for some help for a 2003 Ford F-150 4x4 with 5.4L with a little over 100k on the clock. This truck isn't mine but a freinds that is going through some tuff times right now so I am tring to help her out. The truck is throwing a code of PO172 system to Rich (bank One). I have limited time with it so far but she is stopping back by tomorrow so I can take another look at it in daylight. Here is what I have found so far. I did a fuel pressure test on it to see where the fuel pressure was and it was really slow to come up to pressure. It took 5 key cycles to get it to 40psi. I changed the fuel filter and now it shoots right up to 40 psi with 1 key cycle and runs about 32 to 33 psi at idle and jumps to 40 psi with vac line removed from the regulator and holds pressure fine for 5 min after shutting it off. My guess is this thing has been running like this for a while now. It would eventually come up to 38psi with the old filter in it but it took about 10 to 15 seconds when started. I resest the code with my scan tool and took the thing for a drive and the same code came back. Something else I noticed with my scan tool is the the TPS is showing 18.8% when the TB blades are closed and only 93.4 when the are wide open. Now truth be told I own all GM stuff but all of thier TPS sensors always show 0 at close and 100% at WOT on my scan tool. Is this TPS sensor bad? or is that the way they are on fords? I am going to pull a couple of plugs tomorrow and see what the damage is as far as this thing running lean and I was also going to do a compression test as well. can You guys give some ideas as to what else could be causing this p0172 code? I'm guessing when I pull the plugs it will also help me tell if the O2's are fried. Thanks for the help.