Terrible Smell Hard Accel

[timbstir]

Hi Yarisworld,
I have a 2010 Yaris sedan 5spd MT, I live on the bottom of a mountain road so I have to drive up and down to get to school (grad student), last I started to notice that when I'm hard on the throttle to get up the hill I get a terrible smell. I can't tell where its coming from and it's hard to describe, its not brakes (I know that smell) and it's somewhere between an oil smell and a rubber smell. I only notice the smell when I keep my foot down (basically only going uphill for a long time). I'm not seeing white smoke, or smelling oil normally, and my oil level hasn't dropped at all. Also just clicked 125k miles and switched the spark plugs and didn't see any signs of oil burning on the old ones, so I don't think I'm burning oil in my combustion chamber. Was wondering if anyone has experienced this problem before and knows the cause.
Thanks

[CoryM]

Check for the leftovers of a melted bag on your exhaust.
If it's a manual trans, could be clutch burning. Makes a very acrid smell.

[timbstir]

Nah it's not clutch, I had one die on me before I know exactly what that smells like. I don't see a plastic bag under there either.

[tmontague]

Exhaust leak from the notorious donut gasket that goes bad?

[komichal]

It would be good to stop when the smell is there again. Open the hood and check the engine. There can be some light smoke coming somewhere, it may guide you better. Or you may not see anything there, you may realize that the smell is not coming from the engine... etc.

[nortonfb]

Could it be a critter? Seen it a few times.
Worst was a squirrel for smell. Found on the back of a Corvair motor/body.
At idle the stench was awful, Drive and it dispersed until you stopped