Inconel 718 super alloy turbo manifold studs are highly resistant to corrosion and thermal creep.
Combine them with some kind high temp thread locker and Stage 8 locking hardware for a fail safe solution. (not included)
Size is M8x35mm
Select a set of 4 for your manifold to turbo flange.
Select a set of 5 for your SR20 turbo downpipe.