I've taken those tubes out on a couple of heads, and they whistled at certain rpm ranges. I know that sounds kinda dumb, but the first time I took them out, I searched for the whistle for a couple of hours before I decided to put the tubes back in. The next head I did it on was just to test what happened the first time, and it whistled, too. I tried it on a third head, and it didn't make any difference. Just a thought.
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David
newbie #4153
