Not to doubt Tiger's ability but the weight difference of 2 grams would translate to 0.07 ounces, not 0.7. Even I could tell a difference of 0.7 ounces, and I doubt seriously that Tiger can tell 0.07 ounce difference. I'm not saying it would be impossible, but.....
Remember that "swing weight" isn't the total weight of the club, but the distribution of the weight. A wedge may weigh 50 ~ 75 grams more than a 3 iron from the same set, and they will both have the same swing weight.
Just so you know, a dime weight about 2.2 grams, a dollar bill about one gram.