Head Gasket?

[Ted Schmidt]

When you replace a head gasket what is the general break in time or mileage.
  I just had the had milled like 5 thousand of an inch just to clean it off.
  Also a non-se-r ?.  On toyotas do they like advanced timing as much as
nissan's.  I have a 86 Toyota MR2 base timing should be 10 degree's.  It is
the 4age(4agelc) engine.  Is it worth it to up the timing i run 93 octane no
matter what i spoil my cars.  Plus i'm use to JWT ecu in my sentra.  TIA

Ted in Houston