Your title makes it sound like it is the piggy backs problem. When you bought, they asked you to please go to them first before getting eveyone else chiming in and speculating.
Try their tech call back form? http://www.vishnutuning.com/tech_callback.htm
Please see if you can change the title of the thread until you find out the real root cause of the problem. People will remember the title and months from now and claim a root cause that may or may not be factual.
There was just another person that had a coil problem. The problem would only appear at above stock levels, but a new coil solved the problem.