Remi, its always a good idea to run your car when its bone stock, and in good shape, for 2 reasons. You will gain experience driving and just being in the staging lanes etc. And I know, "you can drive" yea yea yea, its not quite the same as driving around the city, you will learn by driving a diesel Golf automatic for a few passes.
And secondly, you will want a base line for when you modify your car. This way, if you get in 3 or 4 passes and you run a 15.2 average, then you go and put in a full exhaust, turn up the boost a bit and put in a good air filter, then you run a 13.8, then YOU know what that money and time went to on YOUR car with YOU driving. Not comparing what other dudes did.
As for the rain, yea boo-urns for sure. Give the track until about 3 or 3:30, they will make the descision then, its supposed to clear up.