When I bought my GT the dealer had added an VORTEX VALVE option for 595.00. He said the vortex valve would give you an 10% increase in MPG and an 8% increase in HP and that they added them to all their cars. I researched VORTEX VALVE on the net and found that the part was less than 100.00 and the install was simple as pie. The info did say that the valve would increase your MPG but I could'nt find anything about an increase in HP. I find there's a lot of smart cats on this site when it comes to these cars so can anyone fill us in on what I've left out would be a great help. If this is true (you don't think the dealer lied do you?) than for less than a bill you could have a great mod that's quite simple. I have a feeling that there's something rotten in Demark. Thoughts?