My truck runs fine on flat surface but when going uphill and in the slightest steepness, it begins to lose power and I usually have to push harder on the accelateror and this is a problem while being on the highway and having to lose power, I step on the gas and the RMP gage seems to go but it doesn't increase speed,help please! I recently pulled and cleaned out the throttle body, changed the spark plugs and that has not fixed the problem.

It's an automatic

Possibly time for a fluid and filter change. Your description of the problem is not very descriptive though.