I have got a drain on my battery in 98 GTV, if I leave it for 2 or 3 weeks its always flat.
Had 2 new batterys, over the last 5 years, its not that, Alfa GTV mate said his is the same, too many ECU's he reckons !
Plus maybe some anti theft thing, except I think I turned that off !!
No, pretty sure that ECU's are not the problem.
This is a pretty well documented problem and no really definitive answer has been found for every case BUT a lot of times it's caused by the Radio Unit. This is not ignition switched and can pretty much drain a good battery in just a few days. To check this remove the Head Unit when parked up and see what happens. There are other possibilities, if you do a Search you'll find lots of other suggestions.
If it does turn out to be the Radio there are a few ways to rewire it to an ignition switched source to prevent this.
For " real " fault finding, you can do more comprehensive checks. If you are handy with a DMM you can connect this on the Current Range and see what the drain is and if excessive then start removing Fuses until this drops. However not all the Fuses are located in the Fusebox, they are scattered around in some weird and wonderful places. I'm not going to explain this procedure any further, if you get the gist of what I'm saying you'll know how to do it, if you don't understand this it would really be wise, and much safer, to get a 'leccy to do it. If you get it wrong you will be left with charred wreckage of the DMM and Battery and will need to get your underpants in the Washing Machine tout sweet !!
Wasn't aware that you could turn off the Alarm but you can remove it as a lot of people have, me included, as the original Meta system was a bag of poo.
Anyway first steps are to do a Search, that'll keep you busy for a few hours but will give you a good idea of what you are looking for. If you need any more help just yell.