Two of my friends have 20V's in their 86s....both with exhausts and one also with a header. They both put down approx 130whp. They're also both ridiculously loud.

I honestly don't think it's worth the trouble of the swap for that little power. I'd rather rebuild the 16V with forged internals and boost it. It would make WAY more power, and a turbo would quiet down the car immensely.