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RPM tach / gauge jumps

I have a 96 nissan maxima and just yesterday, the rpm gauge jumps to past max at times or displays the rpm as higher than it really is and fluctuates at times. i find that if i take off the bezel by a little bit, and pull on the instrument panel towards me, it sometimes returns the rpm back to normal. and if i push and apply pressure on the glass of the panel, the rpm goes straight to past the max rpm. My actual rpm itself isnt spiking or rough. although, i have less power and acceleration. i have a manual car and normally, in second gear, i can almost redline it and the speed would be at 80mph. but at the times that the rpm gauge returned to normal, i tried the same thing by getting close to redline on second gear but it only goes about 60mph. and when i was on the highway going about 60mph, the rpm is at normal around 2500 in fifth gear but when i floor the pedal, the actual car rpm increases much more faster then normal but i barely accelerate. its like im just burning excess fuel and getting barely any power to the wheels. i recently replaced spark plugs with ngk iridium, changed fuel filter, changed oil and oil filter, and installed new cold air intake. All these upgrades and maintenance was months ago and this problem had just occured yesterday. Can you please help me identify the problem?

Yours is the classic definition of a slipping clutch, and if it’s slipping it’s worn out and needs to be replaced. How many miles on the car?

Try this test: Set the parking brake FIRMLY so the car won’t move. Put the car in 4th gear, give it some gas, and slowly release the clutch. If the engine stalls your clutch is good. If you can take your foot off the clutch and the engine still runs, the clutch is slipping.

The tach needle moving in response to pressure on the glass might be an electrical issue, but the problem of increasing rpm with little or no corresponding acceleration is a slipping clutch.

Ok thanks. I will give that a try.

And in addition, i just checked the obd II codes and i got P0500, P0325, and P0110.
I think i can see that the connector for the knock sensor has a missing wire on one end as the other end, there is a black and white wire but on the end where the connector is connected to the sensor on the engine block, i only see what seems to be a black wire. It could be a white wire thats just dirty and looks black but i cant get my hand in there to take it take it out and see until i take out other parts in the way first. But is it supposed to have two wires running to the sensor? Cuz i think possibly a wire is broken.