Yeah we have two basic stores and like you we changed all our listings over to "FREE" postage about 18-months ago.

Also all the other little things that got us the badge you speak of on each listing.

It all made no observable difference to our search rankings or sales volume.

So its all a big load of hogwash what they tell you and what they actually do.

As far as we can see your item search ranking is mostly dependent on sales volume of a particular item.

For us as an item sells more (becomes more popular) it climbs higher up the list and vice-versa.

Once an item hits rock bottom and nobody ever finds it or buys it then its likely to linger there for a long time.

What we sometimes try is to cancel a low ranked listing and then relist it in the hope that someone filters on new listings and then sees it. That has worked on occsaion too.

When they hand out free auction insertion fees this tends to boost our BIN item sales as we only list auctions in this case (the $1.50 is too high for us to pay normally given the high failure rate).

As auction listings get closer to the end time they climb higher up the result list.

Some buyers will jump into the store from the links on the auction listing.

These are just a couple of the observations we have made that seem to work occasionally.

But how the actual search engine works underneath is really anybody's guess. Even theirs I suspect!

Good luck!