Re: new 156 and gremlins
Rich, your thermostat is definitely shot, I have had to replace mine twice on my car (once at about 70k and again recently at 106,000 miles).
I got mine from Shop4Parts.co.uk, or EB Spares.
Shop4parts was an original Alfa one but still failed again, the EB Spares seems to be a pattern part, we'll see how long that lasts!
As mentioned above, the radiator is the other dead cert to need replacing at some point, they seem to get blocked with s*** between all the little fins and loose efficiency. This will only show up after you have changed the stat, it will then run too hot when sitting in traffic esp in summer.
With everything working coorectly it should run at bang on 90 when moving and go up to as much as 100C (which is almost the next mark up on the gauge), but you need Alfadiag (highly recommended btw!) to see the exact figure.
Unfortunately I don't think it will cure your other problems, I drove mine with the dodgy stat for a few months and the only thing I noticed was a bit less fuel economy.
Let us know what you find on the coik packs...