When we pressure tested the pack after it was removed, it was more academic - an exercise to see if we might find any significant instances of liquid water inside. As a reminder, the process is detailed on Tesla's Service Page . Cover the AGM Silicone Valve on the top of the penthouse with some tape and make sure there are no breathers installed. More than .2 psi will just blow out the umbrella valves. Plug your regulator assembly into the port at the back of the pack, mix some water in a spray bottle with a couple squirts of liquid dish detergent and apply air pressure to the pack. Make sure you cover the rapidmate connections at the back with some tape before you start so they stay dry. Spray your soapy water around the perimeter and look for bubbles. Go over the top of the lid checking each bolt. Check the fuse cover and the coolant rapidmate. Spray up under the rail at the umbrella valves. If your pressure is too high, these are supposed to bleed some air but look for any outliers (i.e. the only one in the row blowing bubbles). You might have pinched an o-ring or there could be some debris in that one.
Chances are good you will get some bubbles somewhere. Remember, you can can get bubbles on a seam or at a bolt head. Make note of where it is leaking and decide the best way to proceed. If the leak is minor, you could try some more sealant topically. If you have a larger area, it may be prudent to remove some fasteners and try to squeeze more sealant in. No matter what, you need to make sure there are no leaks.
When you are happy you have no leaks, put the plug back in the test port, swap out any temporary umbrella valves for Gore Breathers if you are using them and put the covers on the ski rails. You are almost done!