right firstly can i simply take off my td04 and bang on a td05?
also i have a chip in i think mapped for tdo4 so wil my ecu need changing and if so what one to get?

to change the up pipe is it a case of taking turbo out? mines blowing and i have gaskets but turbo bolts are solid to the downpipe so was hoping for another way?

all above on a 95 wrx wagon.

 

if you change to a td05 then you will need to do something about the ecu,i think earlier classics have to have a new ecu or a chip installed as opposed to remapping the original like the later models sure i will be corrected if wrong.
i would suggest soaking the bolts on up and downpipes to turbo daily with wd40 to try and penetrate the rust for a week or so before working on it.
i changed the turbo and both pipes all together on mine but i am fairly certain the uppipe can be removed without touching the downpipe you might just need to undo 1 engine mount and jack engine up a bit to get some room