To get 220 out of an L20 is a top engine and would need this stuff as a min.

Twin 45 webers set up for racing(no air filters racing floats ect)
open exhaust
11+ comp
Custom cam
balanced, stress relieved,shotpend ect
Nismo oil pump, big sump oil cooler ect
All ported ect
big valves 44mm in 35out
good clutch, lightned flywheel

220hp is getting all you can out of an L20.