In a rare change of heart, I'm going to go against what the above folks have said!
I'm starting to think a ko4 swap is infact a good idea!
a ko3S is going to see 230bhp, and thats it. no more. plus, it's not a great power delivery, with a huge slug of power than NOTHING at the top end at all.
Ko3s/ko3 hybrid/ko4 are all going to need a full exhaust and FMIC
If you get a ko3 hybrid, you might get 260bhp as Welly said. You'll never get a 3'' TIP on it though, due to how the turbo sits much lower.
Also, ko3 exhaust housing like to crack, LOTS, even at ko3S output levels. I can only imagine that in the long run the hybrid will crack FAR worse. if that does happen, the only replacement option is another expensive hybrid from CR. not fun. you pay £600 for your hybrid, and bolt it to your almost certainly cracked existing manifold, only to risk it cracking badly down the line with no cheap replacement option. all for 260bhp, 30 more than the ko3S.
a ko4 setup though, can be bought in full for £400-450, and all bolts straight on. You'll need the same MAF and injectors as you would for a hybrid, so that cost is not relavent.
Add in a badger 5 3'' TIP, and we KNOW that setup will easily produce 280bhp on a stock S3 engine, with a downpipe, full exhaust, and FMIC, 290 is highly possible (as many people have suggested from airflows with the 3'' TIP) I would think.
the biggest advantage I can see of doing it this way, is that you're keeping with OEM parts, and if a turbo DOES let go, then you're only looking at £2-300 to replace it, with another direct bolt on turbo.
So, from a budget / future outlay point of view, I reckon the ko4 swap is a great idea for an AGU.
Go back 12 months when ko4's didn't see much over 250bhp before Bills TIP's, and perhaps not so, but with the AGU being large port, and Bills TIP re writing the ko4 rule book, I think it's a really great way to go.
Also, you chaps above have all forgotten that S3/LCR/VXR injectors will not fit Vince's car, as it's an AGU, with different injector fitment to AMK/AUM/BAM engines.
best bet for injectors for that are the Genesis 380cc jobbies from USRT, or if you're on a tighter budget, a set of Saab bosch red tops from ebay for £80 will fit, and I believe are around 340cc.