I noticed the same thing when timing my IP. From my experience, I had a clearer deliniation of flow to drop condition when I had the throttle setting at idle. Full throttle produced an unwieldy flow and I was pumping the heck out of it trying to keep up. I would put it where it works.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.