I have straight piped my 2002 7.3 PSD, the only time it's anoying is when warming it up on a cold day when it kicks up to high idle @ about 1100 rpm if I am outside scraping the wondows, from inside the truck it's not that loud. I agree though, most of the noise is from the engine not the exhaust.
On the other hand my CJ-7 has a 304v8 that I have hopped up, it's fitted with Blackjack fenderwell headers & sweet talker bottles from minute muffler. Now that gets loud when I romp on the skinny pedal.
--Ken
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