Engine misfiring and losing power?

I have a 97 Sentra 160 GSI automatic. We have had motor and head redone, replaced radiator, thermostat and spark plugs but she still has no power. Pls help. She drives decently and will reach normal speeeds but you can't just put your foot down and expect her to go cause she doesn't. We are @ our wits end and don't know wat else to do

Hello, air conditioning was not working well. Only cooling in the morning and evening when it is cool. So upon advice of mechanic, replaced the air compressor. Now it is cooling, but not when it is extremely hot. It also only cools when I accelerate. Also there is a noise coming from what appears to be from the glove compartment box everytime I accelerate. What do you think the problem is?
There is also a loss of significant power when the AC is on.

Just bought a 1996 Nissan Sentra. Runs good but has poor acceleration, and poor gas mileage. (23-26 mixed city and hwy). Who I bought it from told me it just had a tune up, but who can you believe? Could it just need a tune up/new plugs, or something else?
Thanks

I was driving my car at about 40mph when the car overheated and started to jerk violently and would not accelerate. If I released the accelerator then the car would continue to roll and idle fine, but if I tried to accelerate again the car would start to jerk again. The car could still idle just fine but would not accelerate. What could cause this?

It overheated I'm assuming because my radiator fans do not work. But as soon as the gauge went up I stopped and was having the problem, but I'm not sure how long it was hot before the gauge reacted. I always make sure I keep coolant in it since the fans do not work.

I found out that the mass air sensor went out in it. So supposedly that is what was causing my problems

It has a slow response, with or without the a/c on.
It feel like you are towing a car with it, I cleaned the
TBI with carbmedic, and it get better but not at all
could this fault be a sensor or a timing problem?

My 5 speed car had a problem losing power, the it wouldnt idle without my foot on the gas. A friend of mine sprayed the carb or choke and it resolved the issue. Now I am losing power in 5th gear on the highway. I literally went from 65mph to 50 with my foot on the gas! I heard the engine roar but the car acted like it was not getting gas. I went into the parts store to buy and spray the car again myself, but was told by an employee the the parts had to be taken off to clean properly. I am a student and have spent money keeping up the car, so I cant afford to replace it, and I have no idea of where to start to find out what is wrong with it. What can I do to resolve the issue

1994 nissan sentra limited edition- 195,000. When I first got this car it ran great. Recently if the car sits for a long time in second gear when driving the car stalls at 2000 rpms and if given more gas the speed drops rapidly. Also driving on highways between 70 and 80 mph going up any hill the car will lose speed even if the gas pedal is pushed to the floor.

-- another problem- the rpm gauge works unless the car has been driven for more than an hour or if it sits in the sun too long- then the rpm gauge doesnt work at all or drops to zero while driving.

There may be a problem with the throttle position sensor, or TPS. Go to a mechanic and have him plug your car into an OBD reader and see if any codes come up. You can also try this at home if you pick up an OBD reader from an Autozone or Kragen etc.

When I drive my car on the road, I get up to 55 miles n hour and it bogs down to no power until I let up on the gas, then I can drive again. But when it reaches 55 it will do the same thing?