the 1985 cars where hot air cars (no intercooler) they where rated at 200HP. im not to shure exactly what is avaible for you to modify. it is hard to find a bigger turbo for your car because of the design. my suggestion to you is intercooler, SMC alky kit, adjustible fuelpressure regulator and find a way to turn up the boost ( buy a knock detector before you play with that ) but thats where i would start.