Just two years after Texaco settled a race discrimination lawsuit for a record $176 million, it has agreed to pay 186 female executives $3.1 million in back pay because of gender-based discriminatory pay practices. The pay discrepancy was largely among mid-level professionals and executives, many of them in the company's White Plains, N.Y., office. It was discovered during a routine government audit in 1995. The Dept. of Labor plans to conduct 40 more "glass-ceiling" audits of major companies this year.