I'm still suffering the same issue but I cleaned out the throttle body spacer EGR channels, thinking that was it, some guys had the same issue in the Mustang Forums, and that fixed it, but with the Expy same engine, not the same fix, and put that back together about 2 months ago. Last week I pulled the downstream o2 sensors, been driving without since, granted with the Super 44 on the exhaust my Expy sounds mean, but I have less power up hill, and then it's also heating up the heat shielding on the under carriage. Oddly though, after a rain early yesterday morning, I tackled the hill as I do everyday and I didn't lose any power, which is a 1st in a long time, and 1st in 10 days since I pulled the o2 sensors. I was about to put them back in this passed weekend, but one of them had white flakes pouring out of it, so I shook it a bit, and realized something was not right, grabbed a screw driver n spread the inlets a bit, appears the ceramic around the prob shattered, so ordering new o2 sensors soon from Advanvced, now that I found a 20% off code. I'll do the downstreams this weekend, and maybe tackle the upstreams next, but the UP's I never took out. I picked up a new TPS as well, but haven't put it in yet, gonna wait till I do the o2 sensors and drive to n from work for a week, see how my uphill power is.

It almost feels like when it hiccups it's coming from the rear, sounds mad, but that's how it feels 1/2 way up any hill. I have to hit a hill at 2600ish RPM's in order to break 45mph. If I don't I crawl up the hill at 40 and slowly work my way up to 50, eventually.

I spoke to a guy with a 2000 5.4 as opposed to my 4.6, randomly grabbing coffee one morning and he has the same issue. He already had the trans rebuilt at about 80K and is Expy has 140K on it, same as mine, but my trans hasn't given me issue, so I think I can factor out the trans as the issue. Oddly a steeper grade hill, which is very short at that, gives me the same issue, but 1/2 way up, the truck seems to get life out of it, which is what makes me think it's the TPS. I hit that hill at 25-30mph since it's in a school zone, and my power comes all of a sudden 1/2 way up. The longer hill I hit everyday near my house, makes the truck crawl, it's longer and only slightly less steep.