I had a similar problem... (As did a friend of mine)
Driving down the straight, then a loss of power for a second, then back to normal.
For me and my friend it was due to the some of the screws on the lower deck coming into contact with the ground..
I kept an eye on my screw and noticed that everytime my car started glitching, the screws had come loose...
I changed to my graphite lower deck and didn't have a single glitch! (Not that i needed too, i just wanted to anyway)
I guess you could try changing the ride height too, just to isolate the problem..