Indexing slow on column which is not unique? There is a index for code and date columne but it is not unique. Average need 4 minutes to get data. How to improve it?

EXPLAIN ANALYZE select * from timestockdata where code ='3182' and date>'2013-02-04'
"Bitmap Heap Scan on timestockdata (cost=7300.98..714088.30 rows=235409 width=439) (actual time=524.998..208243.496 rows=238866 loops=1)"
" Recheck Cond: (((code)::text = '3182'::text) AND (date > '2013-02-04 00:00:00'::timestamp without time zone))"
" Rows Removed by Index Recheck: 5361451"
" -> Bitmap Index Scan on timestockdata_index (cost=0.00..7242.13 rows=235409 width=0) (actual time=508.144..508.144 rows=238866 loops=1)"
" Index Cond: (((code)::text = '3182'::text) AND (date > '2013-02-04 00:00:00'::timestamp without time zone))"
"Total runtime: 208382.950 ms"

CREATE INDEX timestockdata_index ON timestockdata USING btree (code COLLATE pg_catalog."default", date);