How much off the mark are we talking? If the drills are aligned correctly, you don't have a bent axle, wobble in a wheel, etc... then:
I would say first roll it down the tuning board and take notice of how fast it goes. Remove the wheels, blow them out with air to get rid of potential lint. Set them in a dust free container and reapply the jig to your axles. That means spraying them with brake cleaner or something strong, do a once over polish with the selvyt cloth and final axle polish, clean them off again. Hold the can of jig out at an arms length, spray the mist on there just enough to cover the axle. I hold them horizontally and do a half spin as I am spraying. Let them dry for TEN minutes. Use a magnifier to make sure they didn't collect any LINT, because that is your nearly invisible speed killer if you do not do this. If lint got on it, hit it with just enough of an air blast to get it off of there. Do this for all of the axles. Apply just enough oil to the axle to say it made contact with the whole surface. Slide the wheel on. If you think you applied too much oil, just slide the wheel away from the axle head and back. There should be a glob of it there. I just wipe it off with my finger. Try rolling it down the board again and see if there is any difference. It helps to have another car to run next to it for comparison.