Yeah, not real cheap. Of course it doesn't seems like 200hp+ in a mk1 ever is.
The exchange rate is bad right now. These are made in Europe so it would cost more just because of that.
Anyway, there was a cheap turbocharger manifold on ebay for $120. Looked like it would clear the firewall:
eBay Motors: Toyota Corolla AE86 4AGE Turbo Exhaust Manifolds (item 300178273630 end time Dec-11-07 08:40:21 PST)
Cheap turbo charging for the 20v