1999 Chevy Malibu acceleration

i recently noticed that my engine would sound louder while accelerating,,, especially when i push down on the gas pedal,, and especially while pulling out onto the highway trying to get up to 65 mph.\
prior to this happening, i started to notice a new smell in the car especially while driving for a while on the highway. it wasn't antifreeze that much i know,,, it smelled hot and dry, almost reminded me of brake shoes,, but i've had that checked and it's not that..
then came the acceleration problems.. now it's all the time,, more noticeable when the car is hot.. and the rev noise is louder and almost sounds like an exhaust leak right under the engine, but not while idling,, only when trying to accelerate... i just had a full tune up done,, i've changed the catylitic converter,,, i just had a new muffler put on,,, a new belt.. a new water pump.. none of these things have solved the problem...
i thought maybe it was the transmission,,, and since it's sealed i can't check the fluid level,,
i did notice that i had overfilled the oil by almost a quart,, and it's been a month since i had checked it...
any suggestions on what i should do here,, it's driving me crazy