True anti-lag would upon activation:
1. Open up a throttle bypass (you can use a Ford idle bypass valve for example) to get more air into the plenum when the throttle is shut.
2. Inject a corresponding amount of fuel
3. Delay the igntion timing to the point where semi combusted charge makes it's way past the exhaust valve...using the combustion process to spin the (delicate little pathetic) turbine wheel on the (skinny little slender) shaft which in turns spins the compressor wheel generating boost.
The downside is your cast iron and cast aluminium combustion chamber is no longer where combustion takes place - your (relatively weak, thin walled, fatigue and temperature cycle sensitive) manifold is left to bear the brunt of this bastardized combustion.