Well it seems no one has posted this yet, so I will.
Its in this months OPM, how to get to the secret strip:
To reach the hidden drag strip at Leguna Seca Raceway, you must exit the track. To do so, enter any race in Arcade mode at Leguna Seca Raceway, in any car, perferably all wheel drive, such as the Mitsubishi Lancer or Suzuki Escudo Pikes Peak Version. At the starting line, drive forward until the line is about 2 or 3 car lenths behind you, Then do a 180-degree turn, so that you are facing the exact opposite direction. Drive forward in the new direction. Then, up against the wall on the left hand side, you will see a gate that juts out from the wall. The gate is at an odd angle, about a 75- or 80-degree corner. Drive directly into the corner where the wall and the gate meet, and keep it floored. Turn the wheels back and forth, left to right. Keep doing so until the car begins to go through the wall/gate, and then contine doing so until the car is completely behind the wall. Note: Do not drive back to the track, if you do so you will have to repeat the trick. Turn to the left once you are through the wall and trace a path along the outer perimeter of the track. Pause gameplay, and remember the exact spot abovethe letter "U" in "Continue" on the pause menu. If you draw a small dot on the TV screen with a crayon, it will clearly mark the location of the drag strip. drive toward that dot. Keep driving until you get close to the dot, then slow down. To find the drag strip, slowly turn the car left and right until you see something resembling the walls and outer perimeter of the drag strip. Slowly drive toward the walls. If you continue to drive around the oter perimeter of the drag strip, you will find a way inside, letting you drive on it.
Wow that was alot of typing...
I still have to try this out