18 year old comes in with angina symptoms, they have, ecg, stress ecg, cardiac mri&mra, echo, 24h ecg. would you suggest non-cardiac cause mimicking?

Yes: The above test are enough, if negative, to say that the chest pain is not from coronary artery disease and/or any other structural cardiac disease. Chest wall pain/ costochondritis and acid reflux causing esophageal spasm are two possibilities that can mimic a cardiac problem.

Yes: If the ekg didn't show any signs of ischemia then that 18 year old with normal testing as above could have many other possible illnesses; including reflux disease or esophageal spasm.