I was on 120 ml methadone, i have qt syndrome, after tapering down to 30ml the levels have still not gone down, is methadone the cause then?

Long QT Syndrome : If you truly have long qt syndrome, then it's most likely due to a congenital etiology as opposed to an acquired one such as from methadone. Regardless, you should not be on methadone. At 30 ml, can continue to taper to zero (ideal), or transition to Buprenorphine which is not arrythmogenic. And most importantly, consult an electrophysiologist.