Hey Guys weird problem, i was driving round yesterday then suddenly noticed that my turbo wont spool up in first gear, if i put my foot flat down from stand still it will but if i take off normally then try and boot it my car will only get to the point where the boost is about to kick but it wont its like driving a NA car. Once i change to 2nd or any other gear tho everything works fine...... 
I have changed the boost solenoid and have a new factory turbo at hand.
Car is a r33 skyline with a k and n airbox filter 70k miles
![Race_Snooze [BANNED]](https://i0.wp.com/i.postimg.cc/fLKMkt8H/ban-user.webp?resize=96%2C96 "Race_Snooze [BANNED]")
Lose the K&N filter. It's screwing up your MAF sensor. Drive like a normal, responsible person. You failed to mention what year it is.
It was like this before I took out the PITWORK filter. K&n makes a stock one out of mesh, and the airbox vent connected is what keeps the stock exhaust note. I have a $500 nissan MAF sensor too.
I want to try a new pitwork, and blow off valve see what happens.