This may be a long first post but I want to condense all the main information and questions right now so anyone can start giving some suggestions and opinions.
Please be patiente and read the entire post 
I appreciate it!
So, here we go…
Considering my Kinugawa 20T prematurely failed last week, I have now to take a decision on the path I want to take from now on.
To decide I had to do a few (somewhat quick and simple) questions to myself.
Question 1 - Going bigger or stick with the TD04 family?
Sticking with the TD04 family will be just the same -> Nice mid range torque but getting out of steam from 4500rpm onwards so I’m decided to go bigger. From my little experience with this turbo, I believe this kinugawa 20T is not able to do 350hp (as they claim) in normal conditions (i.e. without using, for instance, meth injection, better flowing head like RN heads or VVT cams). I believe ARD 20T is also not able to do 400hp (probably nor 350hp as well).
I’ll not talk much more about the 20T on this thread. I’ll leave it for the already created 20T thread.
So, I’m ready to loose some low end in order to gain a lot of top end. Let’s go bigger then!
Question 2 – How big I want to go?
Well, firstly I was thinking about a GTX2867R which would be good enough for 380-400hp. According to its compressor map, for that power range I would be in a good efficiency so this turbo would be a good option for these power levels.
However, and despite I was previously doing great torque with the 18T and 20T (somewhere around 480Nm) I started to wonder if my rods (with almost 340.000km on them) would be up to the task of taking 500Nm to 400Nm from 4000rpm to 7000rpm.
Once my car is already stopped due to the failing turbo I’m now starting to seriously think about dropping forged rods on my engine.
I don't want to be dropping a big turbo and 2 weeks later having the car stopped because of a bent rod.
Question 3 – Well, if I’m going to drop forged rods I can go even bigger. Why not?
Assuming our stock pistons are good for more than 400hp, at this point I started to think about the GTX3071R (with .63 AR turbine housing, internal WG) which should be good enough to achieve 410-450hp within a great efficiency range of the turbo.
So, at this moment I’m starting to look on what I will actually need to achieve a reliable 410-450hp goal with this turbo.
At this moment, the mods I have are the ones in my signature.
So, to move on to the GTX3071R, I’m already planning to do the following upgrades:
1. 139,5mm forged rods and ARP bolts -> I’ve been looking at these BSR forged rods. What do you think guys? It seems a good price and they are located in UE so I’ll not have to pay huge custom duties and VAT as I would have to pay if I would import rods from a non UE country. I.e. what may seem a great rod price in the US it is not necessarily a great price here in UE/Portugal.
http://en.bsr.se/product/conrod_volvo_m63113950001
They claim this “These conrods are the same type that was used when we developed 806Hk engine for Koenigsegg.”
True or not, I don’t know…at least it sounds somewhat interesting
2. New rod bearings. I’ve some doubts on the way to go about these. Should I go OEM, Toga or Glyco sputter?
Furthermore, aren’t toga and glyco a single sized bearings? I think I should check the crank wear first and see if I should get oversized bearings or not. At least OEM bearings have 3 different sets. Standard, oversized 1 (0.25mm) and oversized 2 (0.5mm).
3. Of course, redo coolant and oil lines to the turbo.
4. Considering a custom made tubular exhaust manifold for 2 reasons. First because I’m not sure at this moment if the compressor housing will clear on the back engine mount and second because it will of course improve the exhaust flow. Someone knows if the engine mount will be a problem with the compressor housing the in stock location?
5. Redo PCV system by using a catch can to reduce crankcase pressure. By the way, what catch can should I use? Can anyone point me a good one? And about the fittings and lines?
6. Install the N/A exhaust cam once this is already a bigger turbo (the N/A intake cam I already have installed)
7. Repin flywheel and use 707 PP. Where to get the 707PP…?
8. BMW MAF and 630cc inj (730cc @ 4bar as I have) I already have them.
9. Have my downpipe redone of course
10. New piston rings. OEM rings or some other good rings? OEM rings are up to the job?
11. Further to the pistos rings, should I really get forged pistons for this power goal? It is known stock pistons can take 400hp+.
12. I have read the block cracks just becomes a problem 450hp+/500hp+. Do I really need to shim it for 410-450hp? If so, what material to use and what procedure?
13. I’m not planning on throwing a quaife or grip dif (S70R already has the viscous dif which already helps a bit). I’ll be managing boost and torque at lower gears instead.
I am open to any suggestions on what I should further do (I may be forgetting something) and/or on other alternatives that I should consider.
I would also kindly appreciate if some knowledge members could clarify my doubts above and give me some suggestions on rods, bearing, piston rings and catch can for instance.
Thank you all in advance guys.