Hi DG, kudos for you for having a go at full led conversion, its no easy task in our cars!!
The Canbus system in the Alfa is particularly sensitive and the quality of the can-bus bulbs on the market at the minute is negligible. The internal light upgrade is by far one of the most successful conversions and well documented in the first post of this thread. Other areas such as the front side lights have had some success, but the quality of the bulbs means that you probably will have to replace them at some stage. The stop/tails have two main issues, either no can-bus support or they are can-bus but really dim or even worse, for the 1159 bulbs they don't really have a difference between stop & tail operation so you actually make it dangerous.
The indicators require the load a bulb generates to balance the circuit on the flasher unit so you either have to replace the flasher unit with one that is LED safe or re-create the load with resistors, so even canbus bulbs wont help you here.
Then there are the hard to replace bulbs like the side repeaters, High Level Brake Light and vanity mirror, none of which have like for like replacements so your gonna have to make your own as I have.
Long one short. A full 100% conversion may be just out of reach (the vanity mirror is just not worth the effort). but section by section it is viable if you go with additional resistors.
So far mine has:
Full interior (excluding vanity mirror)
Stop / Tail including high level brake light (see my cylon upgrade thread
Front Side lights (24 LED ones with additional resistors soldered in)
55w 6K HIDs see this thread
And next on my list is the indicators, although I first need to pop one of the side repeaters out and see just how they work! no idea what bulb is inside, what space is there and if its a like for like or if I have to make a replacement. I also have no idea if the canbus sensors are on there or if it effects the overall load on the relay.
Incidentally, best option for quality of LEDs is use CREE bulbs but they are much more expensive and need a different resistance as they pull loads more power than normal LEDs. Also, bulb design is massively important. You have to think about the LED layout on the replacement bulbs to make sure you get the best / most optimal light distribution for the purpose your using it for. An example is the CREE bulbs available. They all have a focussed high power beam so using them in say the front indicator position on our cars could actually cause a dazzle effect to oncoming drivers and also not throw enough light into the reflector housing. There are some CREE bulbs that also have an extra 2w of SMD LEDs around the base that would solve the latter problem but the brightness may be too much. only testing will tell and they are about 20-30 quid each!!!
Also, I have some ideas to make a custom H7 LED bulb that will be more powerful than a HID kit to use as my main beam, but that's a future project, after my cylon brake light, custom DRLs and whatever else creeps in ahead of it!!
Anyway, that's the synopsis of the thread so don't forget to update us with any discoveries you find along the way as a lot of people are using this as a decision basis for parting with their hard earned cash so madmen like us are needed to help avoid bad purchases