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Hi there. Just logged in and saw your question. Do you still need help with this issue? If so, be aware that misfires can trigger the Reduce Power condition as well. What are the current code numbers?
If there was a significant vacuum leak, then yes, it could.
The thing that bothers me is what you had to do in order to install the new TPS. The actuator in the throttle body that pushes the TPS arm should have been in such position as to allow the new TPS to go back on and fit without having to use any sort of tool or metal rod. All of which points to the computer trying to compensate for the vacuum leak by moving the throttle valve to stabilize idle speed.
Let's do this; first, replace the EGR gasket and erase the codes. Next, start the engine, turn the A/C on, apply the brakes and shift the trans to Drive. Let the engine idle like that for about 5 minutes to see if the computer relearns the correct idle setting. Please let me know if that does it.
I see. Regarding the manual, you won't need one to solve this issue as we are professional technicians with access to our own databases.
Back to the problem at hand, which code number was it you were getting? Also, do you have access to a scan tool capable of reading sensor data (PID)?, how about a good multimeter?
OK. P1125 is not a TPS code; it sets when the computer sees the Limit Performance Mode is active. You can clear that code either by disconnecting the battery negative cable (make sure you have whatever security codes you need for alarm, radio, etc. before doing this) or with a Tech II scan tool - code readers can't read sensor data (PIDs).
What might have happened was that the engine wasn't getting enough fuel, which caused the Reduced Power and triggered the P0300 on the second OBD trip.
Biggest obstacle I see in diagnosing and fixing this issue is lack of tools. All my knowledge and experience combined with my desire to help you means nothing if you don't have access to the tools we need, such as, for this particular test, a fuel pressure tester. However, if you go to a place like Advance or Autozone, then you can borrow the tester through their loaner program. What do you say?