Idle bouncing/flucuation when coming to a stop

[tommyp603]

I'm currently Stage 3 APR 2.0T 6 Speed manual

Recent work
New Genuine PCV
New VVT Solenoid (oil leaking out of connector)
New N75
New diverter valve
Upgraded PVC hoses
New valve cover gasket
Coil Packs
New purge canister valve
New turbo crankcase breather tube

Spark Plugs have 4K miles on them

The car boost fine and has no issue idling when starting up and idling.

The issue I'm having is when I'm driving and coming to a stop and shift into neutral the rpms drop to 800 then go to 1200 then back to 800 and so on before it settles out at 800.

I performed a smoke test at the manifold port on the intake manifold and had 0 smoke coming from anywhere. After awhile it started coming out of my air filter?

I performed a boost leak test a few weeks ago because i was slightly over boosting but found no leaks.

I don't have any check engine lights at all.

I do have vagcom and can log anything.

The car doesn't do it every time which is weird but it does do it frequently.

Any suggestions of where to look next?

Maybe mass airflow or MAP sensor?

The car did this at stage 2 plus before i did the K04 upgrade so its been on ongoing thing for a bit now.

Any input is appreciated!

Thanks
T

[Flygman]

You still have the intake runner flaps?
No codes for them?

[CycloSteve]

Did you install the correct PCV? There are two types - one for the early models with the silver valve cover, one for the latter black valve cover. Made that mistake on my son's car, and the right one fixed the bouncing idle.

[80sGuy]

Similar situation happened to me and I replaced the Crankshaft Position Sensor (lower and adjacent to the Oil Filter Housing) and then the Camshaft Position Sensor (upper adjacent to the timing cover) because they both emit the same symptoms.