Delete plates are good for a turbo. Not sure about the UDP's because more load on the engine helps spool a turbo. I've kept my pulleys stock for this reason...not sure if it actually helps or not though
I definetly agree with the first part but I dunno about the second. I dont see the pulleys as "load" on the engine but more of a drag on the engine? I dunno its just what I think I feel as though you would benefit from having UDP with turbo.
I view pulleys as kinda of like a brake on the engine and by putting UDP on its like a less of a brake on the engine.
For ex: when you put them on over stock pullies you notice after install the engine is more revy( if thats even a word) as in the rpms are slower to drop. ( less drag on the engine)
Just my on that thought of having UDP with turbo