Throttle/Idle Issue

Hey All! Just picked up a 2008 WRX with only 900 miles - sweet bike but I'm having an issue similar to what is outlined in the Throttle On/Off Issue post.

Sometimes the bike will stumble very slightly at idle, or throttle response is very jumpy when I'm attempting to idle in first gear. Other times, I'll stall when easing out the clutch in first gear.

TPS hovers around 16/17 and 98, so TPS might not be my issue. I've slightly increased the idle speed, which may have helped slightly.

• Mods I already have:
  Stock header
  Yoshi RS2 Slip-On Exhaust
  FMF Programmer (have yet to verify settings)
  

Mods I plan on completing in the next week to improve performance (and possible fix this issue):

• Ground wire to adjust CO, then possibly increase CO
  Remove AIS and Airbox flapper
  FMF Tuning
  Experiment with airbox door, or replace stock air filter
  

Again, that first gear is really tricky. Would adjusting the air/fuel help me out in this case?

Thanks for your help!