Largest turbo I would put on a stock block is a BNR S4 or GT/GTX3071. I would recommend instead something in the GT28 vicinity, eg GTX2867, GT/GTX2871, CS turbo or BNR S3. The stock block and fuel system will limit you to about 350 awhp on E85 or 300 awhp on 93. All of the GT28ish turbos will...