Car goes in limp mode when seeing boost

GTP - Pontiac grand prix ? Anti-theft system light lit on the instrument cluster ? Try spraying carburetor cleaner into the intake to see if tries to start then . Anti-theft on your vehicle disables the fuel injectors .

the system is in limp mode because of a real problem with either the engine or transmission
have the fault codes read, fix what is found and reset the ECM

If it were mine, I'd want to be very sure what it was and so I always use a Repair Manual I can see and read, but that me.

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Pontiac Grand Prix 2004 Owners Manual Download

No different than the last vehicle problem you had

Need to check for codes & diagnose the system with
the fault & find a problem & make the repairs

Trac Control is part of the ABS Braking System & may need professional tools, to get that modules codes,so save your time for free checking at the parts store, to be told nothing of value there

The ABS system may cause a vehicle to go into limp mode if it is defective. Most times that will happen if your ABS light is lit up on your dash board!

You need to program the ECM to accept the new aftermarket parts to adjust properly.

Hi:
The mass air flow sensor is a round sensor that is mounted in the air intake, between the air cleaner box and the engine throttle body.

Make sure it always gets premium fuel...even with premium and especially in warmer weather the GTP will frequently perform the factory programmed KR (knock ******.) In WOT it is also more susceptible to running a lean condition with stock programming.
Things you can do to troubleshoot the problem and give more consistant performance with the GTP is run colder range copper core plugs and/or any brand of cold air intake, or even a stand alone 9" open element cone filter. Both are better than stock and provide more airflow even though the stock airbox was redesigned in '99. What else you can do is not limited to that but a start. Good luck.

check the fuel pump and lines. look for the fuel filter and see how much junk is in it.