I think that process is your problem. I get lovely, saturated but realistic colors from Portra 400 (and 160.) I don't have a lot of them on my Flickr page, but have plenty of prints I could scan and post. I've never seen colors like that from Portra, at least not unintentionally (easy enough to get in a hybrid work flow, actually very difficult to get such muted colors printing on RA4.) I'm not printing RA4 now either, though I used to and may again. I'm having mine commercially printed.

Here's a photo of my wife from a 645 Portra 400 negative:


Alicia - Troy AL by Roger Cole, on Flickr