Take this with a grain of salt, as I read it "on the internet" but from what I've read there's definately something different within the 05 thru 08 years with the clutch/flywheel. I'm pretty certain it affects OEM parts and it definately affects aftermarket parts. Take SPEC for example, their stage 1 (friction and pressure), for 05-06 works just fine with the stock flywheel, but if you have an 07 or 08 you need to change the flywheel to work with that same exact same setup. Reading in to that one can only speculate that the 05-06 and 07-08 uses different flywheels. There was also a disscusion on another group how even the factory has changed their part numbers and now has to base the replacements off the VIN, there is one part for early 07's and before and one for after. I originally saw this as I'm looking for a replacement for my 06 and was checking out SPEC on eBay, this guys was selling a "used" one because it wouldn't work on an 07, that he had to change the flywheel (item=330257705410). Did a bunch of digging after that and there is certainly info out there regarding it. Plus, it was on "the internet" so it has to be true right?

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06 V6 Vert. Satin Silver. Pony Grille, Roush CAI, Hurst short throw, FRPP Dual exhaust, Roush Styling Bar, SCT with Doug's tunes, 8.8 with 3.73's, GT front and rear sways, Shaftmasters 4" aluminum driveshaft and the "Purple" treatment.