i have a rough idle on my v-6 95' 4.3 vortec. i noticed it after i put in stp fuel injector cleaner in the gas tank. could i have chemically burned something or is it coincidence? also could it be from my k&n intake/gibson exhaust that the engine is taking in more air than fuel burning? there is a sweet octane gas smell too. not the regular exhaust smell i usually smell. could it be an air sensor problem on my intake. OH YEA AND IT TAKES LIKE 4 SECONDS FOR MY ENGINE TO START TOO. A LONG START AND A ROUGH IDLE MEANS WHAT?? please help!