Just bought this truck got a new manifold exhaust on it the engine's quiet ..driving around town it's all good but when you try to go out and get above 45.50 it starts shuddering.like its out of gear ..then it goes to driveing good again ..and then down the road it will repeat itself ..any ideal wat it is

 

Any check engine lights or pending codes?

Check the connectors on the O2 sensors, specifically up front.

It may be plugs or faulty COP. Check the wiring, carefully.

 

Needs new spark plugs and possibly coils.