Bought another car today, setting the 1.8t counter on 3  
Its a 2001 AUM, with a blown turbo. A bit like a real 007 gadget with smoke screen on demand (boost). My wife will be driving it, so I will just install an old turbo that I have left from the gt2860r TT. More downtime for the turbo bus yeah  

Head is ready for mild porting, K04 hybrid is up for sale. I decided to sell the manifold and turbo because I want to step up to a true twin scroll gt3071. Its always more fun to build stuff I think, and the turbo is laying around for ages collecting dust. I have had some interest in it, so hopefully I can sell it soon. Price is 1200€ for the manifold + turbo + gaskets and 0.8bar wastegate actuator, if anyone here is interested. Thought that was a decent price for a custom longitudinal kit with tubular.
Anyways, if I get to ordering new stuff I will update this page. Also I have seen photobucket fucked the internet by removing all 3rd party links, so I will try to relocate my albums to somewhere else.

If someone wants to share their vision on valves...
In the vag tuning scene it is very common that people install stainless or inconel valves when rebuilding their heads. In other cases people are very happy with sodium filled valves and these are considered an upgrade over one piece valves because of heat dissipation as well as weight saving (for example 4g63 evo). Even our B5 RS4 as the same exhaust valves. Now, I am going to install stonger springs in my head in any case, but I am not decided on changing the valves just yet. I feel that both stainless and inconel might be a bad upgrade because of the increased heat that will be put in the valve seat. Weight is less of a concern with the stronger springs I guess. The reason I do the springs is just because of the fact I dont want to use old worn springs and the rev limit will probably be around 8000 rpm (judging by the compressor map).

oh, and its here  
Kind of special compressor wheel on it, looks more like a hta73 clone.. anyone that knows what it compares to?
53mm inducer, 73mm exducer, 77.5mm ett 7+7 24mm blade height 15mm hub

The reason why the sodium valves are removed is because when stiffer springs are installed they are hit harder and sodium filled valves are more brittle.
RS4 is nothing special because the max safe rev limit is 7200 RPM on stock head.

It is actually the intake valves that have the soft springs and give issues, so for an easy RPM bump it's enough to replace them.
Doing it correctly you need both intakes and exhausts and then you need to change the exhaust valves to withstand the bigger forces exerted on them.

I am also thinking ahead on how I am going to get enough LPG in the engine with the big turbo, because the choises on injectors are a bit limited. There are larger truck injectors on the market, but they have slow opening/closing times so I am sure there will be no way the engine will idle at lambda 1. That is no option for me, because I need the car to pass the inspection and also because it is a waste of fuel. The other option is to make a staged system, and I am really considering this. A simple way would be to link the ground wires (trigger) together with the gas injector loom but feed 12v to the second stage from the ECU, for example from the SAI pump. Ofcourse combined with a halved krkte and triggered from rpm or load. Not sure if the gas controller can survive a double injector on a single trigger though, but if not I suppose I could move up to a 8 cilinder controller. There are not many examples on higher power small LPG engines that I have found (in fact did not find any) so it is a bit of an adventure. But I am sure I'll manage, just go step by step.

Yes you are right about choke flow but I should not have issues with my goals for boost. My evaporator is rising rate and I have only 1.4 bar base rail pressure (that should currently net enough injector for 240hp). I have seen well over 1.5 bar boost and no problems with lpg delivery at all.

On the other side I really like the liquid injection concept, and must confess that I did not even consider it yet. Mostly due to the fact I only knew about prins and vialle systems (not good for high power) but after a quick search I see that a lot of companies are making liquid injection kits now. I will look more into it, if there is a 500hp capable external pump kit that might be the way forward..

To add on this after reading on about choke flow, what I have gathered there should not be any problems with injector flow up to at least 1.7 PR (butane).  My current injectors are limited to 4 bar maximum working pressure, so if I want to run 2.5 bar boost I can not exceed 1.5 bar base rail pressure and have a 1.43PR at maximum boost in result (accounted for atmospheric). The Barracuda lpg injectors are slightly better flowing and can handle up to 4.5 bar, so if I would buy 8 of those I could go for 2 bar base pressure and end up at 1.57PR with maximum boost. My reducer can not support 2 bar base pressure though (nor the maximum power output), but I found an Australian made reducer (AMR M7) that is rated for 2.7bar outlet pressure and 575hp. Concluding, there might be some options with vapour injection still that would cost me a lot less money converting, however lacking the nice evaporative cooling you obviously get from liquid injection.

A friend broke a Rosten performance spring at idle on a RS4, this after a complete engine rebuild. luckily, no damage was done.

I had a set of Rosten springs on my 1.8T and they worked phenomenally well. I was boosting 30+PSI on a 60-1 and later, a Comp 5556 (flows between a GT3076 and GT3582) I also regularly wound the motor out to 8000 RPM.

So long story short, I wouldn't hesitate to run the Rosten springs.

Phenomenal build by the way!!!