Hi everyone..first time posting, problem w/ jetta

Im currently troubleshooting a problem on a 01' jetta vr6. Whenever its started up cold, mornings mostly, the car hestitates and stumbles as you give it gas. along with it is a bad rumble sound that comes from the exhaust that stops after 5 minutes. After about 10 mins of driving, its fine. one time it kept doing it for a good 20 minutes. Also, wheverever it feels like it, the car wont shift into 3rd gear, it wont even rev as well, no matter how much gas i give, nothing happens, jsut stays in second gear at about 25/30 mph and it wont move above that- this happens rarely though, whether the car is cold or not. did all typical checks- fluid, etc.. connected the to obc and cleared the check lite that pops up once in a while, made no differnce. the check light is always on though when the car is cold. ..any ideas? any info is appreciated. Thanks, Matt

What code is coming up?

have you replaced your fuel filter recently? how about the coil pack?

Fuel filter was replaced a few months ago.
Can the coil pack cause the problem based on the symptoms?
the code is for the mass air flow sensor, but theres nothing wrong with it.