[aerohead]

I found your car here at EcoModder.com's drag list at the top of the forum.
It shows Cd 0.31, however, I don't know if that required the rear spoiler.
The 1st-gen MR2 spoiler was good for a 10-count drag reduction.
The blueprint for your car shows attention to roof sides camber into the C-pillars. They may already be optimized as they are.
Turbulence and vorticity can rob energy, so VGs, reducing the actual volume of disturbed flow might mitigate some of that to the good, even after accounting for the permanent drag due to the VGs themselves. It's hard to tell without a laboratory environment.