fuel injection cleaner

normally, my engine idels really loud, and hurts small dogs ears. I put some diesel fuel injection cleaner into my 300d t-diesel and its
ideling allot quieter. is this a sign of a problem or does this sound normal? i have noticed a decrease in start time and an increase in miles per gallon (running around 36 i believe). thanks.
regards Guidelines on car buying & selling http://www.zone-car.com
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