CREATE TABLE table_41903 ("Tie no" TEXT, "Home team" TEXT, "Score" TEXT, "Away team" TEXT, "Attendance" FLOAT)

What is the highest Attendance when the away team was Wrexham?
SELECT MAX("Attendance") FROM table_41903 WHERE "Away team" = 'wrexham'
SELECT MAX("Attendance") FROM "table_41903" WHERE "Away team" = 'wrexham'