if you've never driven an alfa how do you know you want one ?
I've bought at least two serious money cars without even driving them and just because I liked the way they look (and am a fanboy).
1). The obvious and correct answer is, yes you should. How exactly they can tell unless forensics get involved if you were in a serious accident I'm not sure. If you are asking me what I would do, then the answer would be 'yes'.
2). As mentioned they are going to be an MOT issue if you do not have one and the car did at manufacture. I'm still new to my 159 2.4 (which I adore I might add) but have had EGR issues with my previous 1.9 JTDm GT. EGR issues on my 159 are yet to be experienced by me. I think with the DPF if you use the car and do decent long journeys there really should not be an issue. For me time will tell.
3). MOT in the future, though many here have EGR delete as part of a map (or on it's own) something I might look into myself.
4). Love the growl of the five cylinder when pushed. Sounds good inside but probably like a rattly old tool box outside
. I'm not sure an exhaust on any diesel it worth it. Just my own two pence worth
5 +6). I have no experience with. Mine has done 103k and I think my power steering pump may be goosed or at least a fluid change is required.
There are buyer threads on this section and AlfaWorkshop have a buyer's guide on their website.