Truck is a 2005 Envoy SLT 4.2, PCM4LESS 87 Octane tune, has a G80 rear diff. When I take off it feels almost like i'm driving across the warning rumblers on the side of the road, or a shudder. Doesn't matter if i'm turning, or going straight. Does it for the first 3-5mph and then goes away. What...