In answer to all the questions;
I'm yet to install the turbo muffler delete as I wanted to test out each item on its own.
Super easy to fit, take out the airbox, remove 8mm bolt from turbo inlet bracket, and then simply twist to remove. Took me no longer than 10 minutes. You also need to remove the rubber seal from the original inlet and use with the new one.
And yes I've kept the original plastic tubing, so the engine bay looks stock.
Had dry-ish roads on my route to work this morning, so once warm I gave her some beans. The car felt alive, its hard to tell if theres any real improvement but I did have a massive grin on my face.