Chris Rogers might be able to help. But it looks like you'll have to pull the door cards off yourself if you want certainty.
Isn't there an Australian Mazda club/forum?
Gap your plugs down to 0.7mm, turn off/disconnect your boost controller, check what turbo you have, if you have a standard turbo then budget for a replacement turbo, if you have an aftermarket one, budget for a new coilpacks + ECU + tune.
It's pretty common on most cars, I think it's a design thing, to stop people running out of petrol. The common thing to do is fill it up when it gets low. Why do you want to run the tank dry? Low fuel warning light usually comes on when the tank has ~10L of petrol left, but this varies with cars.
The manifolds I posted are R31 GTS-R style. R31House make new ones.
IMO, that's what you want. The long runners gives it that awesome sound up in the rev range.
The 6boost is similar. They make high mount and low mount I believe. There is a company in NZ that does a high mount, Sinco I think it is. The one you have is a Full Race manifold?