SlUGGISH!!!!!!!!

Once Again Im Back. I Have A Problem My Car Just Went Weird For Some Reaosn One Day Im Thinkin I Had Got Contaminated Gas Or Sumthin Cus It Kept Makin It Sluggish Or Back Fring I Dont Know. I Took Auto Tech For 2 Years N Planin On Going Back To School To Finish Gettn Certified But I Never Messed With A Cavlier S O Idont Know Much About It I Used To Be A Dsm Owner N Still Am Til This Day I Am Also Owner Of A J-body So I Need Help. I Changed Spark Plug Wires, Spark Plugs, O2 Sensor N Switch To Ultimat High Premium Gas Wi=hich Is 93 Octane I Think. I Fixed To Problem A Lil Bit But It Still Does It When I Go At Like A Speed Of 20 Miles An Pushin On Peddle Very Slightly Im Thinkin Bout Changn My Spark Plugs Again Cus I Dont Like The Ones Dats Int There I Have Auto Lites In Imma Switch To Ngk's Like I Run In Other Car. Any Suggestions On What I Should Do?

nothing like breaking in the shift keys, damn