Infinti I30

I have a 2001 infiniti I30 it had ses light on with p0170 and p0174, took it to mechanic they said it was intake manifold, so replaced it, after being repaired. I now notice that the car has hard slow starts it takes more than one try to start it, also it seems to be losing power, once I reach 60mph it won't accelerate past that. The rpm goes up but car moves sluggish and won't go beyond 60.