First you need to realise diesels are alot more tuneable than petrol turbos.
Also bear in mind that the 180 bhp varinat of the abarth is an already tuned version of the 155 and lessens tuning capability on standard parts. With part replacement you can obviously tune it nice and high but remember petrol engines are not as strong and run hotter so to go with big tuning comes big expense ie new pistons and rods. I'm not too sure on the ability to tune on the essesse kit parts and i'm sure we'll find out in due time.
Yea good point, looks like ill have 2 go for a m-jet