Indoor MX ?

I need help.
I shot a indoors MX event for the first time Saturday. I knew I would have some trouble with lighting. I just didn't know how much trouble until I started shooting. I also put the flash on for a few shots but the haze of exhaust in the building showed up 10 times more with the flash than without.
These are a few of the shots from the event. Most were and still are way under exposed even after I bumped up the brightness. Tell me what I can do to get better shots next time.

ISO 2000
f/2.8
1/160

Use a higher ISO. Your 50D can handle it. 3200 or even 6400 should not be out of question in a poorly lit situation such as that. Better to have a noisy, properly exposed picture than a blurry, underexposed one.

yeah you can always noise nija a ton of noise out of a picture but you cant fix blur

also if you can get the flash off camera you wont see as much of the haze