Hi guys i posted on here awhile ago about my ca 16 engine in my race car fluffing/missfire/studdering as of yet the issue hasnt been fixed since then i have checked the earth straps and found all ok the coil pack is fine i have changed fuel tank to a fuel cell thinking that there might have been some crap in the old tank when i last ran it which was last sunday the car had a few fluffing but then seemed to clear and the car ran without any problem untill the last couple of runs the studdering had returned to a point where the car felt like it had no power then it would clear then it would go into studdering again then clear then back to studdering i went over a bump on the track and all of a sudden the car came to life and it reved out to 7,500 rpm with out any trouble and the it was like a rocket but then the studdering was back thats if you call it that but i noticed the tacho was erratically going from 2,000 rpm to 5,000 rpm anyone have any ideas what this could be its starting to do my head in cheers

I was thinking fuel pump right up until you mentioned the tacho - it's got to be whatever is firing the coil pack, either the ECU or separate ignition module. As a test you could even disconnect the tacho wire to make sure that's not interfering, depends if you take the tacho signal off the ECU or somewhere near the coils.