1999 Toyota Corolla My car seems to lose speed when increas

When increasing acceleration my car loses speed it later picks up speed. Also when driving in traffic, when the first gear shifting to second gear is not smooth it takes a while and it jerks upfront to the second gear. I have recently changed the plugs but seen no change. Should I service the injectors or use injection cleaners and how good is the injection cleaners? Also where is the fuel filter located? Thank you