My truck now has been having trouble accelerating. Whenever the vehicle stops like at a stoplight, it will not want to get up and go, but when it does it runs well after until it gets to highway speeds. It will then shake to what feels like more towards the mid to back of the vehicle. I do know there is an exhaust leak at a flange. Which could go with my lower MPG, it is usually around 20 to 21 but is now around 15 to 16.
It also when I am driving the other day was going 55 mph w/o cruise then just slowed down to 45 mph or so without touching the brake while on flat terrain.

 

Do a compression test, just to get that off the table.
If you have cleaned your MAF, the next thing is fuel pump.

Sounds like a failing fuel pump.

Should be at around 55 lbs.

There is a schrader valve on the fuel rail to check this.