I have a 04 GTP with 106K miles. At 87K I had to replace the motor due to a bottom end problem and have 66K on the new motor. The new motor came online fine with no issues and has performed well. Recently, if I get on her, passing, merging, etc. I get the DING DING and "Reduced Engine Power". Throws a PO1125 code. I can shut it down, wait a minute or two and it starts right up and the check light goes out. The car runs fine (other than bad gas mileage that I haven 't figured out yet), and no other codes or problems. I can even accelerate fairly quickly without any problems. Only when I ROMP on it, it dies at about 3200 RPM.

I suspect its a throttle pos sensor or someting, but its going to take someone better than me to tell me how to test, fix this. Many thanks in advance for your help on this one.
What's the point of having a GTP if it croaks at 3200 RPMs?