Car was cutting off while driving

Mass air flow sensor. That's all I need to say. Get one from a wrecker or buy one from gm, you might be able to clean it with break cleaner. You have nothing to lose. But that sounds to me like a maf sensor. My 3.8 intrigue did the exact same thing. It didn't even throw a code, if I remember correctly. I just figured it might have been some oil from the k&n air filter that got on the sensor. But yah that's what it was. If that's not what it is then look at the fuel pressure regulator. But I'm 80% sure.

Thank u! I if I click on the repair manual will it give me location and description of MAF sensor& how to do pressure check?

You need a fuel pressure gauge, there is a shrader valve on the fuel rail that looks like a tire valve stem, thats the only way to check should be any where from 40 - 55 psi at the rail. Check the vacume line coming out of the regulator if its damaged or collapsed aswell.