I suspect you have thrown too much money at the 'problem' without getting a proper diagnosis. Why did you not let the problem come to you by waiting to see what falls off, or becomes obviously noisier.
We've all had annoying knocks, and it pays to be patient unless it is obviously safety related. I once replaced a knocking front strut on our Skoda Favorit, only to find it was not the strut, but the rear wishbone bush that was knackered...DOH!
If its all safe and passes MOTs then just accept it until the culprit makes itself obvious. Playing what I call 'Parts Darts' and throwing parts at the car in the hope that one of them will cure it is expensive, and as you have found, very frustrating if it doesn't do the trick.
We've had our 156 about 15 months and covered over 40,000 miles in that time. Its not needed anything that any other car would not have needed, and it stands at 85,000 on the clock now.
I'd agree that a 75 is a more 'honest' car mechanically however.
Yes I can see your point, I also like your "Parts Darts" catchphrase, but I haven't just brought a load of parts for the sake of it and put them on the car.
The front roll bar had around 3 inches of lateral play in it, not safe, so replaced with the drop links.
Upper wishbones were constantly creaking, tried to lubricate the bushes, too worn out so replaced.
Lower wishbones were also heavily worn, so replaced these too.
Steering rack - firstly it had excessive play in it, secondly it had a bolt missing where it attatches to the subframe, so this had to be replaced as well.
Shock absorbers at the rear were worn, I also had a front spring broken, so brought a new suspension kit and had that fitted to the car - much cheaper than standard Alfa replcaement. Suspension top mounts were also replaced, these weren't too bad, but cost effective to change them at this time.
Exhaust mounts replaced. Yes, this was another thing to fall off the Alfa Romeo. The back box quite literally, fell off. Obviously had to get that fixed.
Top engine stabilizer mount - the rubber had come out of the metal bracket, causing a knocking, so had to put a new one on.
Track rod ends - OK, yes I brought these because I was running out of ideas, prior to getting the steering rack fitted, so just brought them thinking that the others could possibly be worn out.
So really everything I brought was neccessary, apart from the track rods ends. That was a complete diagnosis, with all them knocks and rattles it was very hard to get to the bottom of - actually, I haven't got to the bottom of it yet because I still have a knock. I'm sorry but when you have driven something that rattles and bangs as much as my Alfa has done, you cannot leave it for bits to fail and fall off - that's not safe, and to be honest, none of them faults (apart from the lower wishbones) were picked up in an MOT test.
I will re-examine the engine mounts, if they are OK which I am 99% sure they are, I am completely baffled. The noise is certainly coming from the front and not the rear, that's all I can give away!