90 corolla diesel engine flush yay or nay

[freebeard]

We've got our ducts in a row.

[skyking]

flushing is not something I would do. It will not magically fix MPG issues. It may possibly kill your running engine.
1) clean oil and filter
2) new fuel filters
3)check pump timing
4) replace worn nozzles

The sludge you are thinking about is just laying there in valve covers and low spots on the head, minding its own business. IF you do manage to dislodge it, chances are good it will go somewhere that will do harm.