Sorry for the Long delay in responding to your questions pesky-Jones. I haven't checked this thread in a good while!
1) if your S3 injectors are brand-new they should come with brand-new seals so no you won't need a new seals kit. And I suppose in an ideal world you might have the special tool for removing the injectors but I just pulled them out and they just push back in so I don't think you really need the tool.
2) & 3) when you remove the inlet manifold three of the inlet valves will be closed and one will be open. At all times in the cycle, three will be closed and one will be open. So thankfully, you don't need to worry about finding TDC etc. To confirm for sure, you perform a leak down test. This involves pouring a small volume of petrol onto the valves which appear closed. Wait about 15 to 20 minutes and you should still have exactly the same volume of petrol with none of it having "leaked down" into the cylinder below.
Then carefully tape over the one remaining inlet valve which is obviously open. And you're ready to crack on with carbon scraping without any risk of it getting into the cylinders.
Then when it comes time you can either turn the engine over by hand (down on the crankshaft pulley) or you can give it a very quick click on the starter motor (as per the video above) to close the valve which was open. This will randomly open up one of the three which you have already cleaned. But it will definitely close the dirty one that you have yet to do! Hope that all makes sense?? In the YouTube video linked at the start of the DIY the dude explains it also...
4) Brass. Yeah. I bought a kit which had a selection of brass, nylon and steel brushes. The nylon brushes were great but not really that abrasive. So they only did light work on the carbon. The brass brushes were great!! They really horsed into the carbon. But they got mangled up pretty quickly. The steel brushes I was too scared to use as they seemed very stiff and abrasive and I was worried that they might do damage??
If I had my choice again I would've bought a selection of just brass brushes
5) This is where the 12V petrol siphon pump that I bought off eBay comes into the mix!! You'll see a photo of it in the thread above.
The 12 V siphon pump sucks all the cruddy, carbon, petrol, cleaning liquid gunk and mess out of the inlet. I actually had an old Hoover to hand which was quite handy also for sucking out any of the remaining dried flakes at the end. Then you use Q-Tips and lint free cloths etc etc to finish up. You will know yourself when it is all clean and you're happy with it.
Basically it is really a very simple cleaning job. The hardest part is actually getting access to the Inlet valves. Once you are there it is just like cleaning anything really. Lots and lots and lots of elbow grease! Give yourself loads of time to do it and you will know yourself when you have done a good job
Just one word of caution. I am pretty sure I noticed absolutely no difference in how the car drives before and after the carbon cleaning. I think the forced induction 2.0 TFSI engine is designed to run with a certain amount of carbon on the inlet valves without any headaches.
I'm not sure that it runs any better with the carbon cleaned off! Unless your build up is absolutely chronic.
I know that in the highly strung naturally aspirated V8 Audi RS4 engines etc it makes a big deal to have the carbon cleaned as it can really hamper their performance. But on our turbocharged engines I'm not sure the carbon is such a big deal from a performance point of you.
I'm still very glad I did the job as I like the idea of the inlet valves being clean. But if you're looking for a performance gain I'd be afraid you might be a bit disappointed!
Hope all that helps, and as stated earlier sorry for the long delay in responding
