have you tried resetting the ECU on it?

Here in europe they suffer from "confusion" in the ECU, just disconnect the battery and leave it overnight, reconnect in the morning and take it on a drive, drive it normally and the ECU learns its fuel delivery etc again, it could just be that.

OR

Have you made sure you have the correct spark plugs?

OR

Have you changed the fuel filter recently?

OR

You could have sticky injectors!

the list above is what normally causes problems on that model here in the UK!

Good Luck! If its none of those above drop me a PM and i'll have a word with a few friends who still drive that model!