For the 1987 model year, Toyota has made the jump to the sports-coupe big leagues by fitting an intercooled turbocharger to the Supra's in-line six.
but the turbo had room to grow. you can hit 13's easy with stock engine/ct26/440 inj. see back then toyota gave you the goods when you bought a supra: a strong engine, a turbo that could push 2x the psi it left the factory at, a very stout transmission. etc. OG toyota hardware -- not to be confused with contemporary toyota and its bmw engines that are made of glass.
but the na is weak sauce and needs a turbo (to be brutally honest). . there is just no way around it.