Yo guys. Question about a little "floating" idle. Im out of ideas and out of patience.

Since I got my 1.8t AUM, I always see a little floating idle needle with rpm constanly between 720-760 (VCDS), never standing still (both PB and LPG, but on LPG is a bit worse), occasionally missfiring (on LPG mostly) and a little shaking engine. Every other car I've driven (either gas and diesel) had very stable and stiff idle rpm. As I'm very pedantic, I was doing maximum effort to bring my idle to such state, but without luck. It's like my point of honor to make it standing still and stiff.

For now what I did:
- new PVC set
- new coolant temp sensor
- new oil pressure sensor
- new timing set also with tensioner and chain
- new fuel pump
- new suction jet pump
- leak test performed, all leaks eliminated, but there were only very minor ones and neglectible
- throttle body adaptation done
- N75 and DV swapped
- N249, SAI, cat and rear lambda deleted
- alternator replaced
- spark plugs and coils replaced (two different sets) with whole new wiring
- battery replaced
- different turbo (k03s)

MAF readings are between 2.3-4 g/s with 0.9l/h fuel consumption, IDLE ignition angle fluctuates between 3-9 BTDC. Idle fluctuates both on stock 150hp ecu file and AUQ 180hp too. Rising idle rpm seems to mask the problem a little but not resolving it.

Last thing I can think of is replacing throttle body (but It's clean and not showing any signs of failure) and MAF sensor (similar to throttle, it does not suggest any failure, engine runs similar with MAF unplugged).

All this and like.. no effect. Like none, nothing, zero changes, null. Still floating at it was from beginning. It does not affect driving or anything but It's just that I see it and every so often the engine chokes and drops rpm a little bit more. Every guy who works on 1.8t and every owner says that all these engines happen to work that way and I should accept it as it is, because thats normal.
Any other ideas or advice? Its just scraping my brain so much

No smoke but pressure test only. Every leak sealed. There were only minor leaks.
Compression test 12-12.5b all cylinders.

Many of these parts were replaced because it was necessary - PVC was thrash and was falling apart from touch, oil leaks, failed tensioner and loose chain (-8CF on 093 group), timing set interval reached, fuel pump was very weak under load, mine old turbo was trash. So I expected some improvements anyway. But no luck.

Lambda factor floats between 0.97 to 1.04 on idle, STFT -3:+3%. I dont know what else is to be diagnosed Any advice?

Got it. Will try do test it till tomorrow afternoon.

A little bump 

nmot_w is selected in logger, logged and visible in both .csv logs as a 13th parameter

EDIT:
I dunno how but I clicked this and that, run ECUxPlot with Win7 compatibility and now I can see data. I attach some sample from rpm readings with unified 700-800 rpm axis range (about 10 last seconds). Lambda 1 target on left, lambda 0.9 on right.

We can see occasional spikes and drops on both targets, but overall, on lambda 0.9 rpm regulation is noticeably tighter, faster and smoother, which reflects perfectly my impressions from inside of my car while logging.

I know that it's only 20rpm range, but you know.. for me it's more about curiosity and being pedantic than making it a huge deal. I can see and feel that my engine is struggling on idle (not much but noticeably) and if I can dig into this problem I will try I like doing such stuff. Many 1.8t owners have similar idling issues and no one is willing to take a closer look at it because everybody else is saying "leave it, dont bother, we all have the same". And I'm willing to change it So please do not quench my enthusiasm

It was BlackT idea to try run rich on idle, which could suggest it's a valve tightness issues so I'm waiting for his opinion And clearly, setting lambda to 0.9 not only let engine run still fine but also improved it's behaviour, so there must be something to it. I will try to play with lambda target a little more and see what happens. no one can convince me it's not worth it

It's definitely existent. And I can see it both in experience and in readings before and after lambda tuning

I'm not sayin it will be perfect, because i over 20yrs old engine. I'm just sayin it is possible to affect it a little, maybe even cure it Or at least discover source of this problem

Yeah, that could be the case. Everything seems to indicate that this is the cause. Nevertheless, I probably won't take the gasket off since car runs fine and repairing gasket because this is a rather unprofitable operation in relation to the value of the car. I would rather try to tune fueling.