Big power is relative to your statement.Both engines are know to make 1000bhp with plenty torque.Neither is better than the next.Its just a matter of choice.
Accelarator cable cud be sticking.The cables unreels itself on the inside.Once your touching the peddle and it drops back,then its the cable.Hope this helps.
51 is the knock sensor code.Check the connection to the knock sensor is good.If it is you mite have to replace it.With it sensing knock it will pull back timing etc to protect the engine.Hope this helps.
The year of the vehicle is important.All the cables are the same length but the ends are differant up by the handbrake itself.94 and up the ends are bigger.Hope that helps.