Fuel injectors could be bad but I'd be certain about the code first. Also, you have an Si with a FICV (fast idle control valve) so don't worry about the high rpm upon cold start up. You could mess with the idle screw and trottle cable if you want it a little lower. As for your speedo gauge not working, make sure the cable is in your tranny tight. Also make sure it's plugged into the back of your gauge tight.