Won't Rev past 3K @ WOT?help!

[Fostang]

This might isn't a 5.0 but still a ford and since there isn't much turn out for questions in the small ponies area I decided to bring my question here. A family member just picked up a 96' with the 3.8 engine. One day while getting on to the freeway to my misfurtune I was using the car the car bogged at half throttle and the check engine light came. It accelerated just fine going down the freeway and everything seemed fine except for the check engine light being. Well back on the city streets whenever I would go into what the car would bog out at the line then catch reving only up to 3K and staying there and simply floating across the street until I took it out of wot to 3/4 throttle and then it would take off if I tried going back to what it would hesitate again but slowing begin to rev. The car and engine look new anywhere you look at it and the engine has 60 k miles on it. I was thinking it would either be the mass air or the O2 sensors. What would be a good thing to do to check whats wrong with the car. Oh and also I noticed that when comming to a stop and applying the brakes it revs up and down. I don't hear a vacuum leak on the brake booster but would this be a good place to check. I really need to get this car running back to its normal state so I can continue on my EFI-T5 project. Any info will be greatly appreciated.