One way to see this in logs is to look for unexpected variance between ps_w and actual boost.

That looks like the turbo is getting choked. I have seen that a lot before .... the intake hose is collapsing or the filter is too small.



Lee

Nah that was not the case... The DV was leaking from the diaphragm into the tip. I reversed it so the rip was now "leaking" into the charge pipe and voila: 2350mbar peak  Now I just have to log again and see where my maf exceeds specified max limit, because I got an intermittent maf too high code. I suspect it to be around 4k, thats where it suddenly stopped pulling.
I ordered the electronical TFSI DV as discussed here from a breaker including the adapter, so I'll put that one in as a replacement.
I must say that the engine is finally showing some real muscle, I am definitely riding the limit of my clutch in 5th gear! Maybe I will tone the spike down a bit, because I dont want to fry my new clutch...  Thats the downside of pushing a heavy brick lol... And I just ordered an LC-2 wideband for my birthday (from my wife's account) 

I'm working on my fueling at the moment, to save my valves. I finally got the LPG delivery down on boost, it's a small scale to balance but I managed to get into the 0.85-1 lambda range on boost. The car is running so much stronger now, its really strange to do it like this because I have always feared running lean because of many horror stories people told me. Turns out they dont know what they are talking about (when it comes to LPG)  

I have trouble connecting my LC-2 on the serial connection, I'm reading out from the analog out. Are they sensitive to which serial usb adapter one uses? I cant connect at all, and on my old win98 laptop with direct serial port it doesnt work either. could be dodgy usb adapter and incompatibility of win98 too... I just ordered a new adapter, hope that fixes my connection issues. Local store did not have them   old school equipment...
I'm looking into EGT probes, my friend wants to make me a small multi function lcd panel to show analog values and egt. The price of the sensor is not the problem, but I dont really want to take off my turbo and manifold to drill and tap it to fit the sensor. Post turbo does not make any sense to me so I'll just wait for motivation  

Here is a small compilation of the bus so far, no WOT pulls or anything, I'll make a power video later when everything is how I want it to be
http://youtu.be/eiTOqlnyD20

Progress on the TIP.



Not finished yet and done with my mig machine (I dont own the tig that I used for the chargepipes and exhaust)

Last week on tueseday I went to the VW dealer in my town, to order the TFSI coil adapters. I had a conversation with the head mechanic, and I showed them the launch control function. They were super stoked about it, and I could leave the bus for its annual inspection without an appointment (mine needs to go every 2 years because it is older than 30years, it was due by the 3rd of March  ). I liked that because I had a trip coming up for the weekend, and then I would know if it was safe to go all out on the German autobahn  Unfortunately there where some repair points, so I picked it up at the end of the day and took her home for repair. One nasty thing was one of my rear tires that had bumps on the sidewall at the inside, glad they found that so I could put on a different set of wheels for the trip. I dont want to think about what could have happened with that tire at high speed with lots of cargo.
I repaired mostly everything on wednesday and picked up the adapters in the morning too:

and fitted them to the engine:


My wife and I left to Feldberg Germany on thursday, I picked up 3 friends and so we had the bus fully packed with 5 persons and snowboarding equipment. Good test for the engine, it was a 750km drive. I drove through the night and we had no trouble with the engine at all, just a bit too rainy for speeds above 140kmh (lots of aquaplanning). I noticed that high load in the mountains (1500m) was not really smooth, I guess that was my max pressure ratio limiter kicking in. But its hard work for a little 1.8t pushing a 2000+kg bus up against a steep hill so overall I was happy with the tune.
Did a couple of powerslides as well because sometimes I had to floor it to maintain speed and when the rpms would go over 2000 the power came in quite aggressive for slushy snow roads
On the way back home sunday we had much better weather so I could keep the speed up a bit more, mostly between 140 and 170km/h.
The police found it "interesting" when I passed them with 40km/h speed difference so they pulled me over.

After a quick check of the car and cargo they decided to let me go so I could resume the trip back home 
I havent tested the maximum speed because we were so heavy, but there was definitely more power available. I think I might be able to get it up to 200km/h.
Fuel consumption was very very reasonable, average 6km/liter LPG (lpg is €0,60 here, regular petrol €1.50 so cost wise I would have to run 15km/liter on petrol  I cant get that consumption even in a very expensive modern car at those speeds, let alone in a bus!)
Tomorrow morning the bus goes back to VW to get the inspection finished and then its free of inspections untill the 3rd of March 2017 again 

I bought a genuine K04-020 second hand, I will take it apart for a good inspection when it gets here, and then see if I can do some modifications to fit it to the bus. I am looking for a bit more power up top but I'm scared to kill the driveability with a bigger turbo. So I decided the k04-02x series would suit best. I didnt want a k04-015 and I dont mind to modify parts to fit it. There's plenty of room so maybe I'll just drop it a bit lower with an adapterplate.
We'll see... If I change my mind its easy to sell it again because these things sell easy 

I read some of your posts that got me on the right track, thanks PRJ! I also bought an EGT sensor that I will mount pre-turbo to get it performing within safe margins. I just need a good mafsensor now, because I cant get my fueling very stable due to swinging maf values. But its around .9 lambda most of the time when on boost, and at 1 for cruising. Maybe just a tad richer than I would like, but thats because my factory o2 sensor is slow, it gives lean readings for too long when it is already richening on the wideband and causes positive fuel trims. Need to deep out my pockets again, so it seems... 

Hmm yeah I've also been thinking about moving it outside of the bay to get some colder air into it, might just add a straight pipe and hack a hole in the firewall. There's not really any space left now, unless I have the pipe run inside the filter. Would that work or just make the turbulence worse?
I read in a Tuning book that the pipe in front of the maf should be at least double the size of the diameter, so in my case about 15cm long. It does not state that the airflow should come from a specific direction, so inside-filter pipe might do the trick.