Hi Scotty, hi all,
As the title suggest, I own a 2012 Toyota Yaris with an 1NR-FE engine (gas 1.33L in line 4) with 140 thousand kms (little under 100k miles).
I have started doing my own maintenance recently. The car has always felt quite low on power. It burns a little oil (like a quart every 2k miles). Lately I have decided to start pushing it a little bit to give the variable valve timing a workout. When crossing the 4k RPM's mark, I get a very strong acidic odor inside the cabin, a bit like sulfur.
Is this normal? I'm thinking maybe it's cleaning out the CAT or something? The car does seem to be feeling a little "lighter", but I wonder if it's just placebo... however Scotty has been mentioning the "italian tune up" quite a lot recently saying it does make a difference... so I hope this is actually helpful to the engine and not damaging it. Of course, only after it has warmed up properly and the oil is quite recent.
Cheers,
Bruno
The car has always felt quite low on power.
I would expect that in an economy car equipped with a tiny engine of about 1300cc.
It burns a little oil (like a quart every 2k miles). Lately I have decided to start pushing it a little bit to give the variable valve timing a workout.
Might not be a good idea to stress out a 12-year-old engine that already has a significant oil burning problem.
When crossing the 4k RPM's mark, I get a very strong acidic odor inside the cabin, a bit like sulfur.
https://www.repairsmith.com/blog/car-smells-like-rotten-egg/
https://www.way.com/blog/why-does-my-car-smell-like-rotten-eggs-how-to-fix/
bmw_guy "The car has always felt quite low on power."
Depending on which version you have of the 1.3L engine, it is rated between 95 to 104 horsepower and between 89 to 97 lb-ft of torque. So, you are not going to win many green light to red light races. 
Your alternator may be overcharging at high RPMs. Get the alternator load tested at any AutoZone. A sulfur smell is definitely not normal. A combination of lead, lead oxide and sulfuric acid are the components of a battery.
