I recently had the intake off of my GXP, the sludge in there was sickening. I run good gas and use Seafoam regularly. Car runs fine but it was a mess, not sure if thjis is because of the Direct Injection or what. I followed the LNF Seafoam directions on Youtube and a ton of crap came out of the car, clouds of smoke, did it 4 times and will most likely do it again. This is not simply dumping Seafoam in the tank, you slowly suck it in to the intake from a vacuum line, it's very easy to do and the car does seem to run smoother.