My changes in the postgresql.conf does not work

I have made some changes in my postgresql.conf, well, I made two changes
in this file. the first time, my queries had improved on their execution
time considerably but in the second change, I seem my queries have not
improved on the contrary they have come back to be slow or at best, they
have not changed in its previous improvement.

These are my changes:

+ shared_buffers = 4GB.
+ bgwriter_lru_maxpages = 250.
+ synchronous_commit = off.
+ effective_io_concurrency = 3.
+ checkpoint_segments = 64.
+ checkpoint_timeout = 45min
+ logging_collector = on
+ log_min_duration_statement = 500
+ log_temp_files = 0.

my max connections are 150

Please, what would be my error?

Thank you for the tips,

David Carpio