Loses power going uphill in 5th gear.

No to the tires. Average RPM's I guess, I just start slowing down and have to go down to 4th gear (and higher rpm's) to get up the hill. But I notice the bogg in any gear when I push the gas pedal down too far. Someone told me it might be an "air/fuel sensor"? Thanks for your reply, btw.

Have you checked your catalytic converter? I've got 306,000mi on my 5.2L 95 ran great around town, idles fine, no stalling. I started getting code 27 injector errors. They checked out okay. On hiway could not rev. Above 3000 would start to misfire and stutter. Lacked power on long uphill stretches. Melted the plastic part of the EGR. That clued me to a back pressure problem I drilled a small hole in exhaust pipe just behind the cat and took a pressure reading. Drilled a second hole just before the cat as soon as I heard the exhaust sound coming from the hole I could tell I had excess back pressure. New cat ordered in the mean time drilled a few holes in the bottom of the cat to relief back pressure!(A no no I know) What a difference though runs like she used, revs past 4k with ease!