Shifting Problems (Not mine thankfully)

One of my co-workers has a 2001 Grand Prix SE and he is having some problems with it. When his car shifts gears it sometimes hard shifts and does not feel very smooth - the RPMs also sometimes climb higher than they should. He described it like someone who did not know how to drive a manual transmission very well trying to shift gears. His car has just over 130,000 miles on it and it is completely stock.

My thoughts were maybe a clogged cat or something with the transmission . . Any other thoughts?

Also, he thinks he has been burning oil. The last two oil changes he had his oil level was very low, but he has not noticed any spots under his car so he is thinking its not leaking.

It's possible the trans has a bad Pressure Control Solenoid: 4T65E Trans Shift Hard, P1811 DTC