I have a 2003 Maxima SE 6spd with 80,000 miles.
Here the problem, when I am in 3rd gear doing 55-60mph the rpm is up around 4-5K.
Usually under these conditions when I tap the acceleration the car would accelerate FAST. You can feel the pull and power. But for about a week and a half now the car given that it under the same conditions as stated above. When I tap or even floor it the car would speed up but really slowly with NO power of pull. The rpm and Miles per hour would go up but very SLOW. Please someone give me some info!!! Thank you.

 

if it only happens in 3rd its not the MAF, it would happen all the time in every gear and you would even have trouble starting. i know ive had a bad MAF before. i would say it sounds like the clutch may be slipping.

do this. get the car to about 40mph. shift to 5th or 6th, and step on it. if the rpms go up and your mph doesnt go up at the same relative speed, its the clutch. ive heard about 5.5's having trouble with 3rd gear too, im not sure exactly what though. check TSB's

 

The 3rd gear problem on 5.5 gens refers to bad syncros and crunching when shifting into 3rd gear so that is probably not it.

Is it throwing any codes?