This page can be found on the web at the following url: http://opm.gov/insure/health/faq/premconversion/21.asp
Will this have an effect on my retirement benefits?
No. Whether you participate in CSRS or FERS, your retirement benefit is based upon your gross salary
Will premium conversion affect my base salary for the purpose of determining my "high 3"?
No. Again, premium conversion has no effect on retirement benefits or retirement calculations.