I ask this because I have not serviced the C4 in my car. Few months back it was completely rebuilt and had no leaks. then I had a foam issue in the dip stick when checking level  and the shop checked it all out, they gave me the 100% OK and it seams to be fine. But with the lift I discovered a leak going on around the pan. I tighten the bolts some, not to tight to dent the pan and the leak seamed to slow down to just the bolt below the vac mod. I found the vac mode to also be somewhat loose, so i tighten it up sung. Tonight after a long drive I looked and it really looks to be the gasket. My question is should I use sealer on the new gasket. I will first make sure the pan is flat around the bolt holes.