The mark 4 Astra 2.0L turbo dielsel engine produced 98bhp (dti), the latest astra dielsel also with a 2.0 turbo engine produces 160bhp (cdti). What differences are there in the engines that means a 60% increase in power and is there anything you can do to get these older diesel engines upto more modern figures and still have room for a performance map afterwards?