My tech recommended two things by way of preventive maintenance. One was timing chain replacement. I've read the countless posts on this topic and have decided to roll the dice and just stay with the original chain.

The other was the replacement of (if I remember correctly) a diffuser ball that is somehow related to the injection system. According to my tech, if this goes it can cause a lot of expensive damage.

Anyone know anything about this? I couldn't find any posts.

Thanks.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Those diffuser balls can cause a problem if they break off, but they normally don't do that on their own. If one is gone, it should be replaced, but I wouldn't consider them to be "preventative maintenance" items.

As you indicate, replacing the timing chain is a similar situation. If it has worn sufficiently or is damaged, replace it. Otherwise, keep driving.

I question your tech's motives here........