There is a generational shift relative to "what sounds good", likely influenced by the popularity of small, high performance vehicles based on Honda Civic and Subaru WRX, etc., and their unique sounds which are completely in a different direction from vintage muscle cars. Beyond that, a lot of vehicle engine sound comes from the intake and face it, today's methods are vastly different than back in the 1970s when big, four barrel carburetors ruled the roost in performance vehicles. So the market for sound now comes from alternative cold air intake (CAI) setups. That's how it is for Jeep Grand Cherokee with the Hemi. The OEM intake sounds pretty darn good (at least mine did to my opinion) when you step on it, but for more growl, folks change out to an alternative CAI. Exhaust systems obviously can play a roll, but still...a lot of the sound happens up front at the air intake.
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The most expensive tool is the one you buy "cheaply" and often...