Sure, but flow is flow, and for all intensive porpoises 300hp of air is going to be about the same whether rotary or reciprocating. And I get that more boost on a factory rotary motor could have been a risk not worth taking, and I get that 300hp is a very reasonable (excellent!) number for that car in that era. It's certainly believable there was more on the table and Mazda had no interest in it. Whatever the case. Turbo technology really didn't start to take off til the mid to late '90s, so it's within the realm of belief that by the time Mazda could have built a single-turbo 13b that delivered the performance they wanted the FD was already EOL. Certainly, any early '90s turbo car would have been built with late '80s turbo technology, and full boost at 3000rpm was more or less the target. Delivering it at 2800rpm was sort of an accomplishment. But Saab (truly) pushed development to deliver peak torque earlier - 2200rpm c1993 - and these days turbo cars are expected to deliver peak torque at 1800rpm. In any case, if the goal is 10 or 12psi by 2800rpm with a 300hp peak, the world is your oyster. The GT3071R will deliver something like 25psi by 4000rpm on a 2.0l. The ball bearing Super60 in my old SPG did 20psi by 3200rpm (on 2.0l). I'm expecting the hybrid T3/T4 in the XR4Ti to be in that ballpark as well, having an extra .3l to help. And those are old, old turbos - ~10 year old tech. An appropriately sized twin scroll on a 13b will not have a problem, and will probably shave a few hundred rpm off the torque plateau.