Stock 2006 auto 30k. Mostly a grocery getter but gets loaded from time to time and I drive it pretty hard sometimes too. Just gauges, gdp filter, and straight exhaust. Truck used to be a little loud but sounded normal. Now the engine does this rattle or tap that sounds like either spark knock or valve tap through a narrow rpm range under heavy acceleration. Have heard a similar noise on a truck with a Smarty but the smarty truck did it over a wider rpm range. I would guess my truck does the noise between 1500 and 1600 rpm. Kind of got me a little concerned or I would not ask. Also when I changed my fuel filters this morning in the stock filter I got two or three very small pieces of metal. Pretty tiny but thought i would mention it. Any ideas? Thanks guys.

 

Just went for a test drive. Floor it and at 1800 rpm it feels like the turbo fully spools and it taps to about 2k. So it's pretty quick. Then it does it again when I let off on the way down from 3k to 2800, not quite as pronounced. Just has been getting more noticeable. Kind of concerned.

 

Sound like the engine is starting to hit that comfortable "broken-in" stage. My '02 changed engine-tone dramatically at 28K miles, and I hadn't done any real towing to speak of. My '04 changed engine-tone around the 10K mark, but I'd just finished a 4000mi round-country trip with a 6K trailer to help the break-in process. I wouldn't be worried about the sound if it's not accompanied by another symptom like excessive smoke or rapidly falling mileage.