Questions regarding this engine

[TurboTegla]

First of all are these engines any good? worth a rebuild(which is expensive here because parts are rare, and not many people know these engines)
My d24tic has over 500K km on it and it has a lot of blowby hot and cold,so much so it actualy affected perfomance so i had to route it under the car,but it has so much blowby even on idle that the smoke can come into the car when the windows are down,and there is visible smoke when standing at red lights.
I do have a catch can installed an the car can get 1dl in 1K km(though when its operation tempeture im giving it a lot)

So are these worth a rebuild and a tune?(looking for 300+hp 500+NM) or should i just swap an om606 into it? The swap would cost around 3-4Thusand euros but it would be reliably 300+hp

Also i have a lot of turbo lag,i put on a boost gauge and it doesn't realy start to build boost before 2500 and barely gets full boost(around a bar)by 3K is this normal?

The picture is before re routing the blow by hoses