Your are correct when you referred to the 1st gen RX-7 wing as "optional"----for this reason the wing has historically not been allowed in ITA ---the wing was a dealer installed option (albiet sometimes before the car ever went to the showroom)----the 2nd gen wings were all factory installed-----i.e. part of the car not an "optional" add on. Thus the distinction-----Toyota MR2's have a similar "factory-installed" spoiler---and these are also typically allowed.