IIRC Kaiser tried spacers of a few different sizes and saw no difference in power.
My idea is to widen the sides on the UIM mouth to allow more room to divert to each side.
A diverter would be nice, but it would use up a large area of airflow space.
Maybe if done in conjuction with widening the sides as to not loose air flow area???
BTW - 99 & 00 SVT's had the DH UIM
