The T28 can be run to 14PSI, thats where it starts to lose efficiency afaik. I have seen a GTIR powered car run 16psi +. T28s with Cams is a nice setup among the FWD SR guys, i imagine it would be a nice Torquey setup on an S13. and with tuning from SS i imagine you could make a little more power. us FWD guys have shit for ECU tuning. Sabri has a GTIR powered Sentra that ran 12s when it was running, and i think it had more to give iirc. so it will do decent i would imagine. Nothing like a GT30 series though. those turbos rock.