P-Asserted-Identity with caller withheld "hidden" calls

I have just read on another post P-Asserted-Identity on Call Forward problem that I may need to delete the
trustrpid=yes
sendrpid=pai
to get custom code working in a dial plan, is this what I am missing?
I cant test this at the minute but just looking any pointers to help solve this.
Thx
D