The best way is to decompress the engine to avoid knock.

If you realky dont want to use mapsensor you can use even TPS but it is not good way.

You can retard ignition when throttle is open more then 30% (more or less it depend when your turbo starts to make boost) and at rpm when turbo starts to make boost

but.. map sensor is so cheap that it is stupid to dont use it, first of all mapping will be much easier with map sensor