Apart from the camshaft wear issue, JTS engines seem to suffer from clogging of the inlet and build up on the back of the valves which leads to loss of power. My Alfa mechanic says this is partly due to direct injection not washing fuel over the valves and cleaning them. He has been gradually cleaning his own engine out by rigging up a simple water injection system, running some of the Subaru inlet cleaner through it and inspecting it with his endoscope camera. As a result it has picked up power, compared to when he bought it last year. He says it is important to change the oil more often than the factory recommends, in order to keep the engine clean and avoid camshaft wear. JTS cars I have driven haven't seemed as sparky as the 2 litre Twinsparks. I reckon Twinsparks have good power delivery. My daughter's 156 certainly does.
2004 GT 3.2 V6, Grigio Stromboli
2008 159 ti 2.4 JTDM Sportwagon, Grigio Stromboli
1989 75 3 litre V6, black
1988 75 3 litre, red, (son's car now)
2000 156 TS 2 litre, Cosmos Blue, (daughter's car)