Hi all. I have a 05 model ba xr6 turbo mk2 has a new front mount hybrid x01 intercooler, weapon x coil packs and new plugs just installed. The car seem too run good up to 3.5k revs than inbetween 3.5k to 4k revs you loose power than comes good after 4k revs sounds like a shudder through the car almost like a coil pack is breaking down any ideas thoughts??? plug gaps are 1.1 and would of thought if it was a coil pack would be happening all the time under load??