Hey I recently required a 93 hatch si. I did a rad flush then decided I would replace the thermostat jsut to be safe so I bought more stuff to do another rad flush. I took out the old thermostat and put the new one in which was a stant 195degree thermo and the one that was in there was stock. I used the original oh ring which seemed like it was in tact just fine. The stant thermo wasn't as big but the metal flange around it was the exact size as the stock one. I replaced and filled with coolant and started the car. I opened the little air by pass valve but the whole time nothing was coming out while it was running and the flow seemed the same, the top tube seemed like it was real flat, with no pressure and it got hot for some reason. Besides the fact it was smoking for some very odd reason (white smoke seemed rich because of bad gas or something off) I only have 118K. If you have any answers to my questions please tell me because I need them, I have to have my car up and running in 1 month so I have to fix pretty much every little thing.