I've read the Superior Millennium flow better out of the box than stock Lycoming. Less expensive too, I believe. If you plan to send them out for porting and polishing (e.g. Lycon), maybe only price matters.
Having read many ECI complaints over the past few years, I'd stay away from them.
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ Catto 3 blade NLE, AFP FM-150 FI, 1 PMag, Vetterman Trombone Exh, SkyTech starter,
PlanePower Alt, FlightLines Interior, James cowl & plenum
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