Can you have a pinched nerve but pass the neurological tests? nothing is showing up on xray or mri

The answer is YES: It's interesting the way you phrased your question "passing neurological tests". Nice. Anyways, a description of your symptoms as to why you or someone thinks you have compression of a nerve or nerve root would be helpful to start with. Such compressions often occur without anything showing up on MRI. X-ray would be the worst imaging modality to use if one were looking for such a thing.

Yes: EMG/NCS can be normal if you have what is called a sensory radiculopathy, which is the pain from sciatica without the nerve damage that can be quantified on EMG. Sometimes Xray with flexion/extension views of the spine will show motion changes that may reveal your issues. See a fellowship trained sports/spine trained specialist that are trained to evaluate difficult MRI findings to help you.