1997 grand marquis

Idk

Good question, could also be excessive exhaust back pressure, fuel supply limited due to a bad pump or plugged fuel filter, O2 sensors not responding correctly as well as any number of sensor problems, grounding issues, etc. I think the first thing to check would be the fuel pressure and flow, then the exhaust back pressure, if it's still acting up then a live data scan should locate the problem.

Where can I find that at under the hood

There is a test port towards the rear of the engine on the fuel rail. You can purchase a DIY kit at your local parts store for the exhaust test.

Ok appreciate it man I know I'ma be spending bout 700 to 800 dollars

At least that, if you find you need parts try aftermarket first, it could save you some money.