Thread: 4T65E Code P1811, hard shifting, along with stalling at idle...

Hello all, I have a 2002 Grand Prix GT 40th anniversary edition non-supercharged... The car has 120,800 miles, is basically stock except for a few small things etc.... I was wondering if anyone could help me with a few questions. I have alot to ask so I guess I will just list the issues.
1. Car sometimes hard to start since it putters and takes a few seconds to turn over then you have to rev to get going.
2. More and more frequently, it will drive fine, then once you put it into park, the rpms will start jumping around between 200- 1200 rpms and this is when it usually stalls... only to be started again and be fine.
3. Car sometimes stalls while driving especially when coming to a stop sign....
4. Throws code P1811 max adapt long shift and sometimes has slight hard shifts through ALL shifts...
5. I had the trans fluid and filter changed about 500 miles ago along with Lucas trans treatment.
6. Because of the stalling, I had the clogged catalytic converter removed and straight piped with a new 02 sensor put in.
7. Fresh oil change about 500 miles ago and nothing was amiss...
8 after all this stuff I've done to it, the problems ALL seem to be getting WORSE!

Now I have read alot on this site about each symptom... with the stalling and fluctuating idle being either bad Throttle Positioning Sensor, Bad Idle Air Control Sensor, Bad Mass Airflow Sensor etc.... The P1811 being Pressure Control Solenoid and Trans-Go Shift Kit to fix etc....

But I guess my question is this... Could a collection of things going bad be causing my Transmission to act up? Could running without a catalytic converter cause unwanted problems? I am very worried since its my girlfriends second car and we don't have alot of money to just go down the list and replace 2,000 dollars worth of sensors and solenoids only to be too late and be forced to shell out 2000 for a new Transmission.... Any help would be extremely helpful!!!!

these are the following things I have done with the car
1. oil change with new filter and Lucas oil treatment
2. Transmission pan drop service with new filter, Dex 6 fluid and Lucas Transmission Stabilizer
3. Cut out clogged Catalytic Converter and put in straight pipe with u-bend delete and new 02 sensor
4. New Fuel Filter
5. Listened to gas tank and heard Fuel pump IS coming on, but don't know if it is pumping correct pressure at all times
6. New Front Right wheel hub bearing assembly/ Wheel Speed Sensor

not many tools at my disposal... I appreciate the response. I forgot to mention I sprayed off the MAF with MAF cleaner and it looked good... but I tried that what you suggested... and I will update soon. thanks!

Any update? I got this code from the dealership and they refused to touch it or diagnose it because we did an EGR delete when we changed the upper and lower intake manifold gaskets. I have an 02 naturally aspirated Grand Prix. We changed the ICV, fuel filter, cleaned the MAF, cleaned the intake air temp sensor. We have reset the ECM and it runs fine for a few days then it won't stay idled after crank. Still has the original cat. This did not start happening until we changed the ICV. We have set the ICV to the ECM using KOEO cycles prior to startup. Any help would be greatly appriciated.