[e_fermat]

Let me qualify my comments by saying there are a lot more experienced players out there than me but one thing I do have is a pokertracker omaha database with 500,000 hands and I can tell you there are few players in the low limits who are winning at any significant rate with a VPIP of 16%. There are some but as you have probably seen, most winning players seem to be in the low to mid 20% range (I'm actually quite a bit higher at about 28%).

Rather than look for specific leaks, why not just take the plunge and open your game wide-open at 1-2 and see what happens. Anytime table VPIP average is 40%+ at a loose/passive table you can limp with a lot of cards as long as you're drawing to the nuts post-flop in at least one direction.

Try these as starting hands and see what happens (from playwinningpoker.com):

"A very general starting point for loose-ish games is: AAxx, A2xx, Ax suited, A3xx, four cards ten or bigger (except trips), KK with two decent cards. That's mostly it, but there are definite exceptions like AKsQs4."

I would definitely add a few others like 234X, 23XX (ds). After you get used to playing a lot of opening hands then you can start adjusting for table specific conditions and players.