Transmission and OBD code P0300

2003 Impala. When driving acceleration at low RPM is great and shifting is also great,but when accelerating at high RPM transmission does not want to gear down properly. Also, the transmission seems to jerk when accelerating and after shifting. The more the gas pedal is pushed the less the car moves. We have changed all the solenoids and sensors in the transmission. We hooked it up to an OBD and it has a pending code P0300 which is random misfiring from the cylinders. My question is what could possibly be the cause of my car not accelerating and shifting properly after the sensors and solenoids have been changed, with this code (P0300) being present?

welcome to AF. try this link http://www.obd-codes.com/trouble_codes/generic/p0300-random-multiple-cylinder-misfire-detected.php the jerking you describe is a engine miss fire that is felt when in the car. or it may be a Hesitation or misfiring when accelerating. This may be due to a vacuum leak, but it can also be caused by dirty fuel injectors, a weak fuel pump (low fuel pressure) or a faulty fuel pressure regulator. It can also be caused my ignition misfire due to worn or fouled spark plugs, bad spark plug wires, or weak ignition coil.
i would swear the the trans in the fault. i went though this with the chev van we had. this link hits the mark. good luck

I appreciate your response. Ive been messing with the tranny for the past 2 weeks and replaced all that I needed to replace and the problem is still happening, so I guess im going to start focusing on the engine thank you again!

Gm was having problems with cats and they extended the warranty to 10yrs 120,000. A bad cat will give you the P0300 and poor acceleration. I can't remember if the 03 model year is covered with the extended warranty thou

I changed my spark plugs today, cranked her up and took her for a drive. There was improvement in the way the car felt but Im still having the no acceleration issue. It keeps bogging when more pressure to the pedal is applied! Shifting seems to be fine except between 2-3, its alittle shaky but all the shift solenoids have been replaced! What else could be causing my car to not accelerate when more pressure is added to the gas pedal? p.s. no codes or check engine light have appeared just yet.

Lots of suggestions have been posted, I would check fuel pressure at this point especially under load and have the cat checked for blockage by doing a back pressure test, 1.5 max.