i just bought NGK iridium spark plugs and put them in my 2006 wrx TR. does anyone know if iridium spark plugs need to be gaped?the guys at the autoo shop said they didnt need to be. now my wrx is bogging out and sounding like its backfiring anytime i floor it. it doesn't do it when i moderately accelerate and the turbo still spools up. the only things i moved to put the spark plugs in was my perrin intake and the battery. i made sure to tighten down the plugs and the coil packs.the only mods i have are the perrin intake and hks exhaust. anybody have any idea what might be the problem?