Look at a owners club on facebook or a website to find out their faults when buying.you may need to join when you have a car though.dont forget bargain classic car insurance if its older than 15 years approx.
We owned one from new for 3 years.
Lovely car, so much character, not that quick but an engine that loves to rev , keen handling and steering.
3 litre V6 is sublime but 2.0 litre is still a nice engine and arguably better balanced .
Absolutely loved ours even if we had a few issues with suspension bushes and the electric hood.
I used to frequent the Alfa owner forum for advice . Find yourself a good Alafa specialist to look after it.
There are still a good number of Type 916 Spiders out there.
As has been said, the 3 litre is something else but the 2l Twin Spark is a decent lump – I seem to recall they may have put the 2l V6 Turbo unit in a few too but could be wrong.
The Alfaowner forum is a good place to start & you’ll find a specific Tech Assistance section here: https://www.alfaowner.com/forums/alfa-gtv-916-spider.155/ which should already have known issues with each model. If not or you have specific questions there’s a wealth of knowledge amongst the members.