need to push the accelerator harder

[Nil]

2000 toyota corolla with 129K miles on it. Recently replaced the upstream o2 sensor, got new sparkplugs and did a coolant system flush. However, since the flush, I have a feeling that I have to push the pedal a bit harder to accelerate off the block.
Can there be a co-relation and what might be a good way to test if something is really wrong.

[fishexpo101]

What coolant did you use? Did you use tap water or distilled water?
What did you replace the O2 sensor with? Brand? Universal or OEM connection?
What sparkplugs did you get? Did you verify gap, even if they said pre-gapped?

Have you checked on the coolant levels in the reservoir (not the radiator itself)? After a coolant replacement, not unusual to have residual air bubbles work out themselves. When you say "flushed", flushed how? With plain water or with a chemical flusher?

For O2 sensors - best to stick with Denso OEM, costs a little more up front, but more than pays off in lifespan and less headaches down the road.

For plugs - best to stick with OEM plugs. Either NGK or Denso iridium sparkplugs. Plug gap should be 0.044".

For coolant - best to stick with Toyota Red coolant (undiluted) and mix it with distilled water yourself. If you have to flush it, run just plain distilled water through the system until the drain water runs clear. Then add half the coolant capacity with Toyota Red Coolant at 100%, then the rest with distilled water - that way you get a 50/50 mix. Should take about 6 quarts to do the whole system - if I remember correctly.

[Nil]

I got all the work done at a local shop - they did put in denso O2 sensor and denso spark plugs.While I am not too sure about how they did the flushing, they did use toyota red coolant.

[fishexpo101]

One try would be to reset the ECM and see if that helps. Swapping the plugs and especially the O2 sensors would alter fuel trims slightly (or a lot if they are heavily worn out or faulty). This would mean that the car is running on "older" settings that might not apply. Resetting the ECM is pretty straight forward - quick way is to pull the negative battery terminal off for a few seconds, maybe depress the brake pedal to bleed off any residual charge, and reconnect. Note that if you have an alarm system or audio system anti-theft system PIN - they will not like this very much. The right way is to reset it via a handheld diagnostic scanner.

THen you will start off with a clean slate, the car will relearn fuel trims and your driving habits. Hopefully would respond better to your inputs in the process.