The real cause of injector rattle?

[pro_steve]

Well I know yours didn't have many miles on the clock but it didn't really look like a low mileage car to me... you never know when you buy a used car. Also when changing injectors, even if they came from a low mileage engine they may have been changed at some point, so it's hard to know.

If you want to test the running temperature theory, why not put a big piece of card in front of the radiator so that the engine gets nice and hot, then see if the rattling goes away? Would be an easy test.

My bets are that a good set of low mileage injectors would make it a lot quieter.

Pre injection is there to 'pre-warm' the chamber before the main combustion event, and it certainly does make it run a lot quieter than if you didn't have it.