well shortly after installing my header (which is now currently in a pile in my garage because its a steamy pile of s***) my car started to "miss" at idle. i say miss cuz the engine sounds more like its letting out big puffs of exhaust out of the muffler. the rpms do drop tho when this phenomenon occurrs. so.. wtf?? any ideas?

 

the header was on the car for a week or so before this started btw