Acceleration messed up after power pipe

I have fitted a power pipe onto my Aerox NS50 2013, and my bike seems like it has restricted itself to 35MPH, however it has jets and rollers. When I accelerate I get the power to go fast but it just disappears and goes really slow again. Acceleration speeds have decreased too

 

Still got the variator washer in there?

 

Is the pipe restricted ? Some new pipes have a washer you need to remove.