A cracked head will "generally' not manifest itself in a loss of power. The crack does not typically lower the compression in any cylinder to the point where a power loss is noticeable. The crack does allow oil to pass to the coolant or coolant to pass to the oil. This is undesirable due to the coolant having a detrimental effect on the journal bearings over time.

There are folks that can run a cracked head for 50K miles or more. The performance is not seriously affected and they simply need to add oil and/or coolant. The longevity of the engine will definitely be affected in a negative way.

The removal of the ALDA may not result in excessive smoke if the driver is not a complete fool with the 603. The only place that smoke will be apparent is from a dead stop with your right foot mashed. Once the RPM's come up...........the smoke disappears. The smoke is not apparent from the driver's seat. You would need a vehicle to follow and observe.