Walt,
At the risk of being repetitive, have you tried RTV at those intersections? A couple of points regarding the application of the RTV: 1) surfaces should be clean and free of oil, 2) there are multiple types of RTV, usually the black stuff from the auto supply works here, 3) "a little dab will do ya" is still correct, 4) let the RTV skim for a couple of minutes before installing the pan, 5) after you compress the bead, dont relax the compression.....we did some tests here and found that relaxing the compression could cause tiny leaks.

mike in tucson