I already did a search and didn't find an answer to this.
1. What is the cause?
2. What can be done to prevent it?
3. How do you know if you have this problem?

 

Usually a poor wastegate actuating system.

Replace that ported wastegate with a good aftermarket wastegate and a boost controller. With your setup I would recommend an aftermarket EMS with boost control rather than a simple boost controller.

Buy a good aftermarket boost gauge. Your stock gauge will not work properly with the FCD. A boost spike is when, while under acceleration, your boost overshoots your boost pressure setting momentarily, and then goes back down to the set pressure. If the boost doesn't come down on its own and continues to climb, then it is boost creep.

 

Thanks.