2004 Mazda Tribute FWD V6.. Its drives fine on a flat grade but At Highway speeds 65 to 70 mph in 5th gear OD.... it will start on a 10 to 15% incline, it will lack power and rpms rev up to 2500 to 3000 to maintain the speed barely.
I have replace fuel, Air filters EGR valve. the 2nd Bank Cat was replace also.
Any idea's

 

If it feels sluggish while it revs up you have a slipping transmission.
It could be just low on fluid.
I suggest you get a fluid change. Look up the owner's manual so you know which type of fluid is required and than request that this type of fluid it put in. Shops are sometimes sloppy in regards of this.
For example if it states Mercon V, than it means Mercon V, not Mercon IV. These are very different formulations.