Seems you can unlock lakeside in the plus version with a simple key combo, thanks
Tetsuya Mizuguchi!.
http://www.g-res.com/Saturn/Sa/SA-SegaRallyPlus.html
Google translate:
trick-capture" information
* Stratos appearance command (KARUMA's information)
in the mode select, X, Y, Z, Y , and press the X, Stratos is added to the time attack. In arcade mode, enter the same command, in the car select, press the left to match the MT of the Celica, move the cursor to the MT of the delta, Stratos and press the right, the left according to the MT of Celica press to Stratos of the aT, Stratos of MT appears and press the right according to the MT of the delta.
* Lakeside Course (KARUMA's information)
in the options menu, press the X + Y
* ghost car
in lap select Time Attack mode, move the cursor to 3LAP, press C while pressing the X + R + Z, press the C while holding down the X + Z
* "treasure" information
CD player song can be heard at (KARUMA's information)
hear the same songs as the Sega Rally Championship.
Actually a pretty good site with non-action replay cheats for lesser known japanese games
http://www.g-res.com/Saturn/List.html
