Is this a common thing to leak on the Ej20 engines i noticed some oily residue around the bolts that secure the sump and around the lip, there is about 20k since rebuild on it and im not sure how long its been leaking, Is it a easy job to fix? I have a twinscroll sump on mine, if i need to remove it, it might be a good time to add a windage tray or better pickup while its off. Any tips are welcome

 

I have done mine (04' Forester) quite lately. I don't really think that leaky sumps are a common problem on Subaru - especially if the engine was rebuild. I have heard they are quite well. Usually people advice to check whether is not leaking from the top of the engine, cam sealers or main seal on the front. Sometime might be a bit tricky to locate the real source.
My only advice would be to use cork gasket. It is easier to seal it that with Three Bond 1215 only. I have replaced the oil pick up as well (genuine one) and oil pick up o-rings, and new bolts.