It sounds like you have a faulty MAF (Mass air flow) sensor. It is the big black square portion on the air tube leading from the air filter to the throttlebody on the intake. If it is an V6 I would also check the distributor since they are prone to fail and quite costly. If it is the distributor go on Google and do a search for Ford Probe +HEI
Probably wheel bearings or wheels are unbalanced
Loose motor mounts.
check the crank shaft actuator?
Check the distibutor model and pickup coil .
Taking your foot off the accelerator.
As the vehicle sits idling the driveshaft is not rotating.
Yes, when idling and driving.
It depends on how long you are idling, or how fast you are going. If you know you are going to be idling for a long time, it's best just to put your car in park.
In order to tell you that you would have to describe the noise and what the car is doing when the noise is made. Are you idling, driving, just turned the AC on? What is occurring and what is the noise? Idling and sounds worse when AC is on. Sounds like it is coming from the top of the engine. Vehicle has 120k miles
Car emissions can be reduced by reducing idling time and by driving at a moderate highway speed when possible. Driving too fast and idling are both wasteful in terms of fuel, and increase the vehicle's emissions.
It's a 1997 Tahoe
It is idling. This is hard for an engine to do smoothly.