Low boost, limp mode only when warm

Hey guys, I have been battling this issue for a few months and no matter how much I search I can't figure out what it is. I really can't afford to throw money at my 2000 jetta tdi as it is the reason I got it, to save money on fuel. So I would like to fix on the first try. Anyway this issue started when it got warm out. It has normal boost and runs good when the motor is cool or if it is below 60 degrees outside. If it is above 60 it will run and pull good untill the motor has been at full operating temp for approx 15 minutes, then performance is considerably weaker although it still drives well, it's when the outside air temp is above 70 when it starts getting weak and it will throw it into limp mode if you step on it. When it is above 80s its no fun to drive, 90s it's a real turd, 100s it's a bigger turd. Cel periodically comes on for a code 17964 control pressure regulation limit not reached. It will throw this code sometimes on start up, and sometimes when thrown into limp mode. Sometimes the cel won't come on even when thrown into limp mode and sometimes the cel will be there on start up and then go away when driving... I find this very strange, any tips for things I should check or do?! Any help would be greatly appreciated

No need to throw money at it, just follow the troubleshooting guides. Most of the things can be checked or troubleshot for free. A lot of people just go off track and start skipping ahead in the process by guessing at 'common' causes when it may not even fit their symptoms.

Two really good guides worth reading 2x each before spending a dollar on parts.

http://forums.tdiclub.com/showthread.php?t=179589

http://www.myturbodiesel.com/wiki/l...roubleshooting-vw-seat-skoda-audi-tdi-engine/

With regard to your temperature related symptoms, have you checked to see what temperatures your ECU is seeing for coolant and fuel temp?
The Coolant temp sensor is two sensors in one body. One signal is sent to the dash to display coolant temp, the other is sent to the ECU for use in fueling calculations. If the ECU isn't getting a coolant temp reading then it will substitute a fixed value in it's calculations.

Yes I had it scanned and temp is reading normal on the Ecu and on the dash. So I'm not sure... I will deff read through those thank you!