Maybe it's time for a M3 F80 LCI, and leave it stock.
Drive it to a shop, sip on your latte with nutmeg whilst it gets serviced and on the way home swing by and grab some chai mix for the evening.
Possibly avoid using a Cometic one unless the deck/head surface are perfectly flat.
I did have a look just then and forgiving gaskets such as Tomei or Nitto don't exist for the FJ20, however the Bar-Tek or Kameari ones look good and might do the trick.