[Spits] High compression pistons and smog test

[Hans]

I am rebuilding my California  1976 spitfire's engine and considering using
Moss's HC flat top pistons instead of the LC (dished) ones. I have been told
that I risk failing the NOx  smog test max requirement. I understand that this
is due to the combustion chamber's temperature potentially exceeding 2500
degrees , which generates NOx. Assuming the EGR to function perfectly and the
fuel mixture to a bit rich, is this still potentially a high risk problem?
There must be a few a guys out there that have been tempted to do this to get
the nearly 20 extra  hp. That is so badly needed.