Trying to eliminate soft limp (N75). Can anyone confirm it is the likely issue based

[kingtr]

on the info provided...

The code is: 17956 - Boost Pressure Regulation Valve (N75): Open Circuit P1548-35-10---Intermittent

I replaced the N75 about 13 months ago.

There is NO MIL, but the car is in soft limp (boosts to and holds 5 PSI). Right when I start the car (first few minutes of driving) the car will boost higher than 5 PSI (which I don't because not warmed up).

Also I noticed that during the day when it is hot it will always stay at 5 PSI, at night when it is cooler it will sometimes cooperate with my request (acceleration) and boost high (spike ~ 18 PSI) if I go WOT, but if I let off the throttle at ALL it will go back down to 5psi and hold regardless of me going back to WOT. Then if I change gears and go WOT again it will again boost high, but decrease and hold at 5psi if I let off the accelerator at all.

With the code already pulled I am quite confident and hoping that replacing the N75 will solve my issue.

With these symptoms are there any other things I should consider? I.e. wiring, but would that create intermittent signal, and the off/on boost based on throttle/temp? Or could wastegate actuator be issue, or would that throw different code?

I just want to check before I go spend another $100 on an N75.

Also "slow response from sensor 1 O2 sensor" code, which I do not believe has any correlation.

Update: Checked wiring and tubing from N75 and everything looks and feels good'n'tight.

[kingtr]

Quick thought. Only thing I've changed in engine bay has been putting modded stock airbox back in (and removing HKS cone filter).

It had HKS 3" outlet cone filter connected straight to 3" MAF into the TIP before and now goes from the TIP into a 1/2" connector piece into the airbox (actually connects to MAF housing which pokes out front of airbox). Other side of MAF housing has 1/2" of tube (which I was told to use to straighten the air). The airbox has K&N filter (I know not good for MAF- all I could find as dealership was closed) and regular ducting to the front of the car. Also left in the custom heat shield (from guy on AZ).

Could this result in heat-soak? Do my symptoms from before sound like heat-soak? The fact it is much cooler tonight and the car is running significantly better has me wondering... Nonetheless, I still have the N75 intermittent code.