I usually use a pneumatic angle grinder and some 3M pads to buff it off. Make sure to Stay flat, go slow, use pressure to keep from spinning too fast(no sparks). But be very careful between cylinders it's easy to slip and round off the edges. No Bueno. Not sure how deep they are supposed to be. Use air to blow out ports and a rag to keep the debris from getting in your mouth (if you're a mouth breather like me. Ha.) or in the cylinders etc. But I've only used this method on cats and Detroits. And what I do isn't always right. Someone correct me if I'm wrong for the 1FZ