Did the kit come with new spark plugs? If yes, are they gapped at 0.032"? If no, check the spark plugs. Buy a set of NGK BKR7E and gap them to 0.032". Second, put diaelectric grease on the coilpacks. Third, pull the MAF and clean it with CRC MAF cleaner.
I have a similar issue. At any gear, any RPM, any speed, if I press the throtlle down hard, the car would hesitate and bog as if it lost power. If I kept the throttle down, it will pick itself back up after about 2 seconds and then take off. However, if I slowly press down on the throttle and the RPM raises up gradually, it would not have that problem. I did the above three things and it fixed it about 80%. There is still a little bit of issue but I'm still working it out. But it cleared out most of it.
