I have a hesitation when its going slower if you give it plenty of gas it goes on but when going slow it misses, ive changed all firing system parts and maf sensor. any help would be appreciated.

It is OBDII - stop buying guessed at parts and have it scanned- LIVE DATA while on a test drive!! That will be the most cost-effective way to DIAGNOSE the cause of the symptom(s). Is it worse after it warms up? Check for clogged exhaust. (hint: vacuum gauge and knowledge of its' use and how to read results is a 'plus').. MAP sensor DATA if scanned , will also be the hint....