usually on that style of gasket it will pull the gasket in or completely blow out the place where there is a leak. What is your vac guage reading under load? Id clean and wipe down the gasket and top of the tank where the gasket meets the tank put it back on fire up the machine put a load on it and run your fingers under the lip of the lid and see if you can feel any air sucking in if you do feel air sucking in then you have a leak. Picture looked like your missing a strip or two of gasket in the middle but i may be wrong its been a while since ive worked on a 405 hope this helps
