bottom end is basically the same - though compression is lower
205 has much better head design - runs map , instead of afm , no TVIS , bigger injectors ( as noted ) a better intercooling system thatn the air to air setup on the 185 etc ..
cams are sligtly more wild on the intake side - but identical on exhuast
throttle body went from a 55mm item to a 65 i think ..
Turbos a fair bit better in design though a ct26 can still turn out comparable numbers when highflowed
thats about i know off the top of my head at this hour of the night