If you want 150hp from a 1HD-T, leave it stock as a rock.
std they are rated at 115kW = 154hp
If you want more hp,
Z()LTAN wrote:fuel and boost
+ 3" mandrel exhaust, intercooler, boost control, hi flow turbo (more air flow + boost)
these mods should see increase of maybe 30% (150kW/200hp) depending on the condition of your engine, turbo, fuel pump, injectors etc
just increasing boost and adjusting fuel pump can see big increase.
EGT gauge is essential if you are going to push it, boost gauge is handy too
Beyond all that ^^^ how much $$$$ can you throw at it.
Some very basic prices below (there is always going to be additional costs for hoses, fittings, clamps, bolts, bits and peices) also if you arent capable of doing alll these things yourself, add $$ for custom installation
gauges ~$500
hiflow CT26 ~$12-1500
Garrett BB turbo ~$1500+
Intercooler ~$500-1000 upto $2500 (+water pump, radiator, hoses, pipe wiring, thermo switches, fans etc, etc) depanding on if you go ebay crap or laminova water to aircooler
3"exhaust ~$700-1100 I built my own 4" dump+3"zorst($700 just in materials)