Car is making a high pitch squeal some times when driving,noise gets worse when I take foot off the gas pedal. Also has odor of boiled eggs at times. Is this a tranny problem or emission system failure or something else.

Possible pilot shaft bushing or throw out bearing going bad.

Sounds like a dragging brake pad. There is an adhesive that can be applied between the calipers and the pads. Or it may be time for a rear end brake change.

I wonder if you have a fan belt that is screeching? They get glazed over and eventually wear out and make a high whine and screeching noise. This might...be what it is

You need to have the brakes inspected. This noise is the brake pad wear warning tab hitting the brake rotor.;

To address your first problem squeaking brakes aka "brake squeal", is most often casued by one or 2 things: "Pad vibration" or a "low brake warning sensor".

Pad vibation is usually caused by ineffective pad anti-rattling clips & hardware that allow the pads to vibrate at a super fast speed whenever the brakes are applied, thus causing a high pitch brake squeal. To correct this, replace all the pad hardware and anti-rattling clips and make sure you use a quality pad set that has anti-rattling plates attached to the backs of them. Weather conditions do affect brake squeal, that is why it seems to be worse at times.

Low brake warning sensor squeal occurs when your brake pads reach the point of replacement, the sensor attached to the pads scrapes on the rotor which produces a high pitch squealing sound to warn you it's time for new pads.

As far as your second problem goes (a knocking sound), I'll need more information about the problem before I can offer a possible cause (eg. happens on left or right turns, while going over bumps, at high or low speeds, accellerating...).

To see if the noise is coming from one of the accessories driven by the serpentine belt, remove the belt and run the engine for a short time. If the noise is gone, spin each one the pulleys and see if you feel any roughness or the pulley is binding. The belt tensioner pulley and the idler pulley are the most frequently ones that cause squealing noise.

Could be the squeler on the brakes. Does that to let you know it's time for brake job. Have your brakes checked

Ignition system sounds probable on vhicle when everything gets warmed up. High pitched hum could be bad tire or worse bearing.

Hi there, you are right... the squeeling from what you explained is the throw out bearing or release bearing .

loose fan belt?

Put the car in neutral, set the parking brake, open the hood, get someone to listen/see where the sound is coming from, as you press on the accelerator.