've got a honda 2004 with a rough idle and misfire, changed the sparks & triple checked the coils & replaced air sensor. Cold start up vehicle is terrible but after Engine warms up you would never think that it’s has rough idle or misfire. I used to run car on the regular petrol with no problem but now I’m using supreme because this seems to run smoother on the engine and less rough idle. Next I will look a vacuum leak or gunk on the throttle valve but can’t see how this would effect the fact that after warm vehicle runs fine, Also I’ve noticed I’m not getting the same pressure release when I remove fuel cap and I feel this is where the problem is. Any ideas on how to approach?