Does severe mitral regurge overestimate ef? If echo shows improvement of ef 45% after being 26 & 32% post mi, is this real? What is the real ef?

Of course. Any mitral regurgitation after a mild degree (even moderate, in other words) will falsely improve ef as the ventricular force will take the easy way out (through the valve and into the low pressure left atrial space). The real ef has to be calculated based on an MRI possibly, echocardiography is a poor measure of true ef under these circumstances.