R34 GTT ecu plus Nistune with the right base image is another way to go if you can't find another stocker.
I am pretty sure the base images include 800, 801 and 802....from memory.
If you are talking about a low mount cast manifold I thought they already come with the correct stud holes for a T4 and all you need to do is refit the studs.
I am sure my manifold has both.
The hypergear hiflow you have linked might suit you perfectly but there is a monster hypergear thread, perhaps spend some time reading recent results and you can pick the best turbo that suits your application.
250rwkw = good result on 98 ron
E85 won't need a total fuel system upgrade just a decent E85 safe fuel pump would be all I would do.
300rwkw was done on one of the dynos in Adelaide from memory......but I have a feeling it would make 250rwkw on the same dyno you used.
Western Sydney is awesome for cruising slowly in the morning and afternoon peaks.
It just occurred to me that the FIA might have made changes to the phasing of traffic lights on the way to work in the last month because they have made a bearable situation 3 times worse.
Pretty sure Fineline had a number of issues with them and swapped to 3240's to get around the plastic bearing cartridges....but the memory isn't what it used to be. A search in this forum should find it.
Don't over oil them, spray some electrical contact cleaner on the AFM wire when you change oil.
There is no problem using K&N filters. There may be better options out there but if you have one then just maintain it correctly and it will be fine.
Pay Scotty for a properly designed and made intake pipe.
Just over 2 weeks until Melbourne...
Watching them cruise around slowly, conserving fuel, is going to be hard going.
Practice 1,2,3 at turn 1-2 will be the highlight IMO the rest is shaping up like a solar car challenge.