2003 Suzuki Aerio hesitation on acceleration

Hi guys, i recently did a minor tune-up on a 2003 suziki aerio with 66000 miles on it.
I changed spark plugs platnum with the 2 tip, changed the pcv valve,changed trany fluid and air filter.
I know noticed the car has hard time speeding smoothly at low speed but it operates great at high speed, it drives perfect in the highway.
what could it be about the car not functioning like it supposed to? is the 2 tip spark plugs not recommeded for it? or what?
please help.
Thanks in advance.