Sounds like my first turbo engine, a 4G61T. Had a "reputable" garage do the conversion in my CB lancer hatch. Went like a bomb until it started cutting out and misfiring. Took it to a different place and they put in on the dyno. They shut it down when didn't stop boosting and found the watsegate was permanently shut. Was a bit boring after that but it eventually spat a valve and that was it...