Just ordered uv dye and a uv light. Time to get to the bottom of this

put dye in system, still no sign of a leak.

may not but does the intercooler spray pipework head any wear near that? (i have a wrx not a sti)

The bonnet isn't down when the smoke/steam is coming out. Im starting to wonder if the exhaust manifold is leaking

That sounds a bit fanciful (although I apprecate you're clutching at straws!). The exhaust manifold may be leaking, but it won't be leaking water, directly, as it isn't water cooled. The nearest it'll get to having water in it will be if there's some immediate post-startup condensation. It'll then burn off as the engine warms.

From what you've said elsewhere your coolant level is dropping, quite quickly isn't it? In danger of going round in circles here as this has been going on so long, but have you positively eliminated the head gasket on that side as a potential source, either for a coolant leak out of the water jacket to the outside of the head, or tested for the presence of combustion gases in the coolant?

I have tested the oil for signs of coolant dye. There is no sign . Thankfully, i have checked the coolant in the header tank after starting the car , it doesn't seem to be going down. Is it possible to put some kind of dye pellet through the air intake/exhaust system to see if the manifold to turbo seal is leaking . Thanks to all for posting.