Hi, long time lurker here and have been looking everywhere for a fix to this problem but have not had much luck.. car is a 2000 civic si (american ex) with a d16y8, 220k on it. it stutters really hard under low throttle and feels like there's a little kick every couple seconds.. engine feels like its not as free revving as it used to be. kind of feels like there's something holding the engine back when you get on it a little and finally when you hit about 5k it feels and revs out normal. sometimes after turning the car back on for a short period of being off ill set off in 1st and the car loses power entirely for a couple seconds and then jumps back up. i can rev it out and that helps it get back to normal but it struggles to get there. if i keep her up in the revs it runs great. recently (5k ago) put in new plugs, wires, dist. cap and rotor, got newer injectors, cleaned them and put those in, still no difference. did the fuel filter as well. car has an aftermarket header and cai. header does not have an 02 sensor in it which i think is kind of odd but not sure if it would make the car run like this. i know this topic has been posted lots of times but many threads did not document the fix. thanks in advance! will also add that it idles normal pretty much all of the time, had a real low idle a couple of times but not too recently.