Man there is a lot of ass talking in here. I'm almost certain all of you have no clue what driving any race car is like, let alone what a difference 100 pounds can make. I can't stand Robby Gordon, but he has a point. He's just saying what the other drivers are thinking, but don't have the cajones to say. IRL is one of the few racing associations that doesn't weigh the cars WITH the driver. It just makes sense to weigh the cars with the driver.
I drive NASCAR modifieds, and believe me, 100 pounds makes a difference. In some divisions, including my own, 50 or 100 pounds is a weight penalty given by the rules for using a different engine or carb. For example in my division at certain tracks a 2 barrell carb is mandatory, but if you do want to run with a 4-barrell, which adds significant horsepower, you have to add 100 pounds to the car to even it out. Also, there are some divisions that give one weight, say 2800 pounds for a "crate engine" or 2900 pounds for a "tour legal" engine, which makes quite a bit more horsepower.
So, 100 pounds DOES make a difference. It's ridiculous that IRL doesn't weigh with the drivers like 90% of other racing associations.