zulu, why is the fact that your dealer-installed filter is an E-Core a problem for you? I realise that it's the same technology as in a SuperTech filter, but aren't AC Delco filters made to GM's spec? I mean, Champion makes both SuperTech and the factory-installed Ford filters, but I would have to think that the filter they provide for Ford is made to Ford's specs and therefor is of more than adequate quality.
Just because something is GM spec doesn't mean it is automatically okay. Dex-cool is GM spec too...
It's not just the nylon core, its the cardboard endcaps, etc, etc. I realize that plenty of people haven't had any issues, but the same can be said about Fram. IMHO it's a step down in quality/construction, which is not typical for any AC Delco branded filter.