[RD CHILI]

Hello everyone, this is my first post and I need a little help.
My 04 GT is in the shop for the third time for the same problem, (error code P1188)Turbo Overboost. When this happens the car surges at idle and on decelleration. PCM was replaced twice. This time there supposed to find out what's causing the module to go out, we will see! Has anyone else had this problem on the 04 GT?? If so, what was the cure? The only mods to the vehicle are BTG cat back dual exhaust and a K&N drop in filter. The first two occurences happened before the mods. Hope I get it back for the Block Party. Thanks in advance for your replies.