Lean condition.

[Beemer]

Hey guys, when I run my turbo timer my idle stumbles a bit, idles low and runs lean.I have a wideband installed. I bought the car with the timer already installed. Just wondering it its a improper install. Its a 96 silvia sr20det. it has 550cc inj. and a upgraded fuel pump. Also not really a big concern but my car idles at about 1k rpm all the time and it makes a little pop noise sometimes and idle is a bit rough as in it noticeably idles up and down by the exhaust sound. Not sure if a iacv would cause that or should change a fuel filter. Plugs are practically brand new. Any info would be great thanks!