the standard 1.8 TD p100/sierra doesnt have an intercooler.
putting one on will help a fair bit.
you can turn the fuel and boost up, put a big K&N on it, big pipe and and an intercooler but you will probably only see 110bhp
i turned the boost and fuel up on one and ran it with a down pipe and an old group A filter from a cossy and i only had 97bhp :/