i was wondering if someone was going to touch on that too. i disagree with the lack of top end with a big exhaust. in fact, it's totally the opposite. small piping will give good torque but squeeze airflow up top. no good.
i say check those plugs <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt='

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Eric