I have a nissan b14 with the ga15de engine. It had the stock air intake system from the throttle body outwards replaced with a cone filter and flexible tubing. I noticed that more recently, when accelerating, especially around 2 RPM, the needle and engine rev's would fluctuate about 2 units on the tachometer and I would hear the engine speeding up and slowing down accordingly.
Also, sometimes when at stop by a traffic lights and I pull off, about a second after, the rev's would drop to below 1/2 and behave as if its going to cut off, even though the pedal is depressed. It would recover on its own after about a 2 seconds.
I was told that if i wanted it to work as it should I have to revert to the stock system as the car is receiving input from the sensor that would normally be on the stock system.
Can anyone offer some advice on what to do please?