It is actually very simple. For the drivethrough exploit simply enter the pit-lane and go back out the entrance. You have now completed your drive through.

The same principle applies to pitstops and stop&go's, the difference is that you have to stop in a pit box and serve your penalty/fix your car.

This exploit is only really useable on track where the pitlane entrance is very close to the track. Like on westhill.

It might no be very practical and you would probably be banned if you were found using it but it is still an exploit.

Done in P8.

have you tried it with autokick=on?

I'm guessing you are referring to driving backwards?

In that case you don't drive far enough backwards to get kicked.

Yeah you don't drive backwards far enough to get a kick. This is pretty bad, seeing that Westhill, SO Long, BL2R, some Aston tracks, and Fernbay tracks could use this exploit easily.