Did you pressureize the FFIM or the entire system when it was bolted on Ive seen flanges warped causing a similar sound from not sealing properly to the head.
yeah mine whistles at idle (throttle cracked open) and at low throttle/hi vac situations. 10 in/vac and boost it doesnt whistle.
larry at sp said the ford isc ports on the bottom might be causing the whistle. so might try to fill those in instead of using a block off plate later down the road.
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