Expensive/complicted solutions probably do not help much so here is a simple one. Like you I fitted a deep sump kit. It came with a
horizontal baffle but the Instructions were wrong about where to fit it. I fitted it in the correct position and the Instructions were changed.
If your kit does not have a horizontal baffle - try one? If it did come with a spacer+horizontal baffle- where exactly did you fit it? Imho it should be above the spacer. The Instructions said below. Now they are "above".Makes more sense to have the much deeper insertion of the pickups.But if the vertical baffles leak....
Did you use the 997 pickups+extenders?
Did you use s/s vertical 'flaps' in the vertical baffles ? The plastic ones flop around and warp so do not seal well.
Investigate the heat exchanger delete plate + a dedicated oil cooler .Vertex sell one.
http://986forum.com/forums/boxster-racing-forum/65050-heat-exchanger-delete-oil-cooler-added.html