Can you twin turbo a Subaru sti?

The way the EJ engines are designed, and the engine compartment of the STI itself, is specifically suited to fit one turbo. But, anything is possible with custom fabrication. Doing something like twin turboing an STI though would cost too much money, you're looking at over $20k.

It would be a much better choice to simply put a larger turbo on. Less money, more simplicity, more reliable, easier to work with, probably faster as well.