So update....have now finally done the exhaust, had it done by Van der Linde systems, some pics:
Will try and post some pics of the system when I have the car in the air again just to show the absolutely perfect workmanship, everything pretty much looks like a OEM system in terms of quality and workmanship only difference is the mufflers.
Some videos;
Before:
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After:
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Exhaust was hot in both cases.
In terms driving the sound is subdued under normal driving, but has a very nice deep aggressive tone when prodded, which for me is perfect. It has tones that kind of reminds me of both s50b30 and s38, but with it own unique sound that I have not heard on a 330i before.
Performance wise it feel the same up to around 3500 RPM from there it feels like the engine opens up a bit, it gives the slight feeling of and engine with a cam where the power delivery was very linear before.
There is also a noticeable improvement in terms of throttle response.
For anyone looking at having very high quality exhaust work done (and willing to pay the price of course) I would definitely recommend Van der Linde systems, some of the best workmanship I have seen.
Their website for those interested:
http://www.vdlsystems.com/VDLSYSTEMS.HTM
(I have no affiliation, just posting to share info)