This is what is they list on RockAuto for the 15-20WRX with a turbocharged FA20 engine in it. I think it's the FA20D engine, but a lot of parts are showing FA20E and FA20F as I peruse the different sections. They are out of stock so no price is shown, but they do share the part number.
Mahle/Clevite 745TC23593000
Chasing the part number, Autozone has them for just under $1k. You could call the wrecking yards and likely find one, but the intake plumbing is quite different on that car vs the 86. Also, that engine is at a little lower compression as well, I think 10.5:1, but that won't matter. If you're committed to the junkyard parts bin, find the FA20 turbo charged models and start looking. Kinda looks like it may just be the 15-20 WRX that has it. The STIs bump to a 2.5 liter powerplant. I thought there was one in the Outbacks somewhere, but a quick look proved me wrong.
https://www.autozone.com/external-en...000/187601_0_0
Good luck.