since I've done lim gaskets, new (stock..bosch wires I believe) and new ngk iridium plugs, I've noticed a slight shutter when starting to accelerate. Even in park it does it. Not a motor mount, and everything was done by a certified gm mechanic that has hundreds of lim gaskets so im confident the procedure was done correctly. Im wondering if those plugs are creating the problem? Its not a huge problem, but something I've noticed since the change.