Adaptronic ECU, turbo from anywhere (i recommend a gt28rs), pwr charge cooler, or front mount, custom piping, BB manifold, custom downpipe. either skim the pistons to lower compression or go wossner ones. Small bits like 3bar map can be picked up from certain cars. and then just small little connectors or oil feeds etc
adaptronic ECU is 500+ or there abouts, turbo was about 800 i think. CC is about 300 if you sources pump and pipe elsewhere. manifold 300. pistons, 400. then lets say plus a couple of 100 for the rest of the small items where you can find them cheap. in total about 2.5k if you do the work yourself. Buts thats if you want to go for a decent conversion. can get a lot cheaper if you go elsewhere. 2nd hand turbo, front mount etc etc. can do conversion as cheap as 1k i recon if you know where to look