Hey Fast and Steve,
I myself own a '91, been in my family since that date, and been in my possession for 4 years. Let me start by saying that in 4 years I haven't really found much either but don't give up. There is a great thread on Nissan Forums on just the KA motor with comparisons of single and dual overhead cams, turbos, and why nos is so horrible for this motor. A custom CAI helps the car breathe and is simple to create, just go to Advance Auto (or whatever you have around you) and by a cone filter to replace the stock air box and some universal piping. ThePartsBin.com is another great place to look around, I just bought new NHT powdercoated calipers and EBC Rotors and Pads from them and I noticed they have a ton of stuff from exhaust to suspension and in between. I know it may seem pointless to try and make this car fast because its FWD but think about how fun it is to drive such a light weight, quick accelerating vehicle. If you want a simple answer to your question, just Google KA24E Turbo and you'll see some stuff but good luck getting it to work. If you want any other info I've come across in my 4 year search just send me a PM.
Good Luck and Go Fast!
i know the thread is old but really i think making a turbo stanza is quite possible. S13 guys favor the SOHC KA for boost over the DE, and using RWD parts you can make it happen. what you need is a basic T2-series Log style turbo manifold, then get a FWD T25 or T28 from SR20Forums, a Front mount intercooler kit, and a custom down pipe/exhaust. as for computer tuning, i'm sure JWT can tune a computer for you.