Make sure the power delivery from the engine is smooth through the rev range especially between 2500 to 3500 giri under different amounts of throttle i.e. make sure the engine does not lose or gain power momentarily. Sometimes these issues can be easily fixed, other times anything but.
JTS engines have quite a few rattles; many normal e.g. pcv valve (after throttle body), variator and flexi exhaust section. If it sounds highly like a diesel the variator may be on its way out, if it rattles in the rear muffler and from the exhaust manifold the catalytic convertor could be buggered (there would be an engine light however unless it had just been cleared).
If the clutch takes inconsistently, especially after a long run the master or slave cylinder may need replacing. You can check the master cylinder by looking for oil on the cylinder above the clutch pedal, don’t be put off if you have to replace it but do be put off it is the slave (inside the gear box).
The best advice I can give is to take it firstly for a long drive on the motorway get it fully warmed up (close to middle engine temperature gauge line) then take it around town or suburbs, stopping and starting a lot whilst driving through the lower rev range. Let it idle for a while, my JTS can be inconsistent on idle but if it sounds like it wants to die walk away or else you will have to go through what I did.
After letting it sit for a while make sure there is no water leaking from the radiator. There may be a bit of oil on the oil sump which is nothing to worry about if it isn’t dripping as the seal around the dip stick can leak which is easily fixed.
I believe a well maintained car will have smooth power delivery through the rev range, will idle nicely and have a clean engine bay. Also don’t be put off by any rewiring as I would be surprised if the wires hadn’t been touched at some stage.
My own car a 156 JTS makes a knocking noise from the front over bumps as the sway bar bushings are a bit lose but I can’t be bothered replacing them as they do no harm. I have heard that suspension squeaks can be wishbone bushings, but don’t confuse those suspension squeaks with the dash which can also squeak.
Have a look at this post I wrote: http://www.alfaowner.com/Forum/alfa-...-problems.html
Don’t be put off though as Alfa’s can be good cars and I have had a lot of enjoyment out of mine.
If there is even the slightest doubt take it to a knowledgeable
Alfa mechanic to look over as it could save you a lot of time and money in the future.