Sluggish feeling on Take off and when Cruising

Hey guys I'm hoping to get some help or advice. I've been having this problem with my truck for a couple of years now. When I go to take off, whether it's in the morning, middle of the day, or at night, my truck is very hesitant to take off, until I floor it, then it takes off without a problem. I have changed spark plugs, changed engine and transmission oils, checked for vacuum leaks using starter fluid, but nothing has fixed the problem so far. Its got 145K on it but it started having problem back at, I wanna say maybe 80k-90k.

Any help or suggestions would be greatly appreciated. Thanks

 

Have you changed the oil in all the Difs?

 

No I havent. I didnt even think about that. My problem seems like it would be a performance issue more likely. when i take off lightly my engine is very shaky and hesitant. Its hard to really explain.