Hey guys I'm new to the forum and needed some help with an issue I'm having with my Passat. First the details on the car:
2006 Passat 2.0T with 61k miles with current up to date maintenance
Everything is factory stock on the vehicle except for the wheels. I have aftermarket 18x8 Moda wheels with Falken ZX19 tires.

I have been having issues with the vehicle vibrating slightly at 50-60 mph, but between 60-70+ mph it gets worse. However when I throttle off the vibration stops at 70 but when I accelerate it starts to shake again . I've had a new set of tire put on, rebalanced the wheels five times, alignment done three times, and have confirmed with three different shops the the tires and wheels are not out of shape. So, I'm stumped and can't figure out what the problem could be. I was looking around and some people have noted that the axles could be out of balance.

If some one could give me some advice I would greatly appreciate it.