89MustangGX said:
Interesting, my long tubes were quieter than my shorties, and I've heard that it is not uncommon.
I agree, but let me ramble on a second...

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My situation was, 1-5/8" long tubes vs stock shorties, and it was definatly more audible after.
now, compare 1-5/8" shorties to 1-5/8"LT's, and the I agree LT's will be be less harsh on the ears.
I've never seen dba tests on the two setups, but, it's my belief that one is no quieter than the other.
I "think" that shorties produce a raspier, more hysterical sound that is just plain harder on the ears...
Where LT's produce a deeper, more bass-y authoritive sound...
My "opinion" is, shorties are like listening to a cheap radio, and LT's are like listening to a good home stereo...
Now, I thought my car was more quiet after the LT swap too... and asked my wife her opinion, which was - it's definatly louder but sounded better. She said she could hear the car comming from much further away... but that was compared to stock shorties.
again, all subjective.