Violent surge after installing intake

Hi everyone,

This weekend I serviced my car (oir and filter, fuel filter, cooling system needs a cleaning and I'm waiting for my hoses to arrive so I can change everything) and took my time to swap the OEM airbox for a cheap chinese filter and a 3" pipe I had lying at home. I had already had the filter directly on top of the throttle body and I felt the car more responsive, but in 4th and 5th gears it was loud as hell and gave me a headache. That's why I decided to add the piping, hoping it would muffle the sound a bit.

The setup I went was this. I know I have to cut the pipe shorter, but didn't want to spend more time as it was already 4 pm and I hadn't eaten since 8.30 am.


My first objective is achieved, the sound is nice and bearable at WOT. However, I'm experiencing heavy surge at said full throttle. It's more noticeable at 2nd and 3rd gears, but cruising at 2800 rpm on 5th gear I can feel it if the load changes. I plugged the thin tube that goes to the bottom or the airbox, but nothing changes. I'll probably go back to the filter on throttle body, but I really want the car to be quieter or I'll just stick to the airbox.

Any idea on why it's so shaky now? I've seen many intakes in the forum and most seem similar to my layout. May it have to do withe the fuel system? I'm almost sure I mounted the filter top side up, but I guess I can check that by intalling the OEM airbox. Help appreciated.

EDIT: I tried with the small tube blanked and also left open, but always over the intake. Installed the filter directly on top of the throttle body and had a less frequent lighter shaking, but it was still there. Then took the plug from the small tube, moved it to the front between the battery and the fuseboxes and it works flawlessly now. I wanna try to have the steel pipe and the silicone piping with said thin tube opened and moved to the front. I thought it just went to a temperature valve and from there to the canister, but I don't know how that would affect the intake performance.

Could someone enlighten me on the function of the small tube that goes to the airbox? How does it affect my setup?
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