I have an '05 Baja with about 175K. Recently started getting some bad vibes on the highway after the car had been drive an hour or so. It almost felt like driving over one of those "wake up" rumble strips--you could really feel it through the steering wheel. I figured it must be a tire/wheel/suspension problem but when I let off the gas, the vibration stops immediately. So, I am thinking it is actually an engine problem...any ideas?