The very first mods before anything suggested above:
Get decent quality EGT and Boost Gauges!
If don't know what your boost and EGT's are doing then you flying blind. It doesn't matter if a DI or CRD.
ZD30 killers:
High EGT's, puts holes in pistons
High Revs (they pull well to 3000, not much point revving anymore)
Poor maintenance
Simple mods I have found good and well documented everywhere in a basic order:
- Boost & EGT gauges (avoid petrol engine EGT gauges, get one that goes down to at least 100°C, Boost is good to have range of 0-20 or 0-25 PSI)
- Zorst, 2.75 - 3" (straight through systems do and will drone, a muffler won't hurt. CAT's can be "Lost")
- Oil Vapour catch-can (ProVent 200's are great and mount up near ABS unit/Vacuum lines)
- Dawes Valve and/or bleed screw, 16PSI is a good level, any more is really wasting power as you are not putting in anymore fuel (Careful with CRD's, they get fussy when VNT solenoid not in control)
- Block the EGR
- Fit better air cleaner element, factory kill turbine whistle and is a choke point.
- Induction tube replacement helps as well, smoother airflow
- Better inter-cooler for sure, fan assisted for anything moving slower the 50Kph
- If you are mechanically minded, pull the entire induction tract off and clean it
- If after all this, then look at chip works
DON'T fit a stainless snorkel that faces the rear, forward facing @ 100Kph can see an extra free pound of intake pressure, facing backwards robs power at speed. If you don't like mud in it, undo hose-band and face to rear while in muck!
Leave the Swirl valve system alone, it helps with bottom-end torque.