i installed the infernos without the fc and it ran fine, it did seem to run hot and didnt sound very great when id engine brake. i left the stock gaskets in and just bolted em' um, no leaks... but then i realized i forgot to put in the "power cones" so i had to take them back off and now i have a small leak.... im gonna take them off here in about 20 min, flip and rotate the gaskets, then bolt em back up and see how she works lol. Also i put in the cobra fc yesterday and really didnt notice any change, i didnt mess with the settings but i dont think its running lean so im not real sure what good adding more fuel will do me, prolly just take it to the shop sometime and have them mess with it..
Oh and if you havent bought em yet, these pipes are LOUD, like, really LOUD