I have a 2001 grand am gt

What I do bout that

A common problem is that the throttle housing needs to be cleaned. Disassemble the plastic housing from the air filter to the Throttle. then go get some carb//throttle cleaner at Auto zone......and some Mass Air Flow (MAF) Sensor cleaner as well. I used two cans on mine and then make sure your throttle is open while cleaning the back side of the flap. All this black build up will come pouring out. Now mine runs great. You have to do this every couple years. Hope this helps

Listen for hissing or whistling or air sucking sounds, or use carb cleaner or map/propane gas un-lite (not lite up and engine running and spray around vacuum lines and intake to engine block gasket and listen for rpm changes.

Can use soapy water and spray around looking foe bubbles (like when looking for leaks in a tire)

Wait how I do that I don't get it

Use a spray bottle with water and little bit of dish soap/liquid hand soap and crank engine up and spray generously around the intake gasket and anywhere aound the engine bay that has a vacuum line running to it and the entire vacuum line and look for changes in the soapy water like tiny bubbles or blowing the soapy water of the line or sucking it in it. Or use the map gas and valve with a extension tube so you can reach in close to the tight places and crank engine and then open the valve and point it around those places mentioned above and listen for rpm changes most times it will go up in rpm but can stall out too which may seem to lower rpm if its not quite enough to stall out. Or carb cleaner way crank it up and spray those places and same as the map gas way, listen for changes, Also look online or youtube for more info as seeing it done on video can benefit you.

Of course steam machine either rent or buy or make one and can do this better for finding tricky leaks. But this is also a guess to your issue you may just need a full tune up or clean the throttle body or IAC valve which can be done with throttle body cleaner and new gaskets just take them off and clean with nylon brushes and reinstall. Plugs & wire set may need replaced, how old or dirty is your air filter. Have you ever cleaned or replaced the PCV. if do so. Are there codes set, scan computer for codes and check all possible reasons that code or codes can be set before buying the sensor that set that code as it just reports a problem and likely is fine and the system it monitors needs servicing.

Also just because I know these cars have head & intake gasket issues from factory I would test for coolant loss and do a compression leak test and exhaust in coolant test and coolant in oil test to be sure its not a gasket issue, which could make the engine run bad too.

A lot of times a high idle issue means a vacuum or intake gasket leak but could be other issues too. Like the mentioned above.

It was running bad at 1st then I took the mass air flow sensor loose and it run good but sometimes it cuts off and idle up

I'd think there is a connection that it is bad or another part in conjunction with the readings the MAF sends its signal to computer then it sends commands to another to keep everything running smooth. May not be a bad idea to clean with MAF cleaner (do not touch filament) and try it again hooked up. I still think you have a vacuum leak, it is possible the MAF is bad, but with it unhooked the computer is forced to run in failsafe/limp mode so this means that you could have any issue possible and it is running in limp mode for sure now and is covering up the issue as best it can which also means locating this issue if its other than vacuum leak and is electrical issue or sensor problem almost impossible to locate, so the only thing you can do is look for vacuum leaks then if none use multimeter and check all sensors for correct readings and check the codes and follow up with new test for each systems code that is set. Maf could just be dirty or bad or may not have anything to do with the MAF. I would find & fix vacuum leaks and if you have found some and fixed hook Maf back up after reading and recording all codes stored in computer, then re-seting the computer and crank & drive and see if check engine light comes back on or runs bad then recover the code and go from there, I would also use some electrical computer board contact cleaner on all electrical connections you can find and clean them and use some dielectric grease on all those connections before plugging them back up, also do the same on the spark plug boots. Crank the motor up at night to see if your spark plug wires are arching on the each other or any metal as this is a sure fire way to see if your plug wires are bad. pull the plugs and check them too, replace if look bad or burned , you can test them but the basic OEM ac-delco brand are so cheap and OEM too, I would just replace them.

I'm lookin for a leak but I don't see nothin

I said steam before I meant smoke test, can help find vac leaks. Otherwise I would get a repair manual and start testing procedures on all the components until you discover the issue.