trouble shifting, when i get on the freeway and step on it it is pretty slow and sometimes it stops at around 60 and take a while to get any higher or if i am going up hill and step on it is pretty much a struggle, it wont go any faster then 50mph and the rpms will be at 3000 and then shoot back super fast and i start to slow down. also my check engine light is on and the code is p0128. Please help

 

Please provide some vehicle specifics...

P0128 - Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
This indicates that the thermostat is likely bad.

Your condition sounds like a restricted catalytic converter.