Toyota 4WD Surf Owners

So i recently picked up a 1kz Surf, all running well and perfect until the was a bunch of black smoke kicking out the back
It got me seriously worried as i'm really tight on money and this is pretty much my dream car. I had the injectors changed and that cost near $600 and although it reduced the smoke it's still present.
The spill valve (or so i think) on the injector pump is pis***** out diesel and the exhaust smokes alot when cold but when warmed up runs better but still smokes a fair amount more than it should. i've got a spare one and not sure what condition it's currently in but im not too hopeful as it was off a wreck - Any suggestions as to what i can do? is there any other cheaper injectors pumps that could work on this model? its a 95' - I'm not mechanically minded really so I'm not sure if there are any options of what i could possibly do to save money as i'd really like to keep her running!
Thanks