Everybody will whine about the platinum plugs but I would check the firing order again first. Cylinder #1 is at the front of the engine. The firing order is written on the black plastic plug wire cover on the valve cover and should be 153624 with the number 1 wire being located at the 1 o'clock position on the distributor cap as viewed from the front of the vehicle. If the engine ran fine before you "serviced' it you must have cross wired the plugs. Mark