renault laguna losin power?

have a 03 laguna that has given me nothing but hassle, the turbo went in dec(turned out it was to small for car)had it replaced with reconditioned one then, altinator went and then it started losin power occasionally which has become more presistant and the turbo lights came on today but when i turned off the engine and turned it back on they had gone off.

pat
January 2011