Burning carbon smell?

Definitely not a valve cover gasket leak. I know the smell of leaking oil burning on an exhaust manifold. The only oil leak this car has is internal. It starts around 2-3k after an oil change. When it gets a bit low, I add some 20w50 until I can get around to changing it all. The car is old and runs non-stop for several hours every day. Otherwise, it starts pretty clean and there are no spots under it, even if it sits for days. Every mail route car I've ever owned (that's a lot) has burned oil.

I'm thinking a large piece of carbon buildup broke off (or is breaking up) somewhere and is burning up in the exhaust. If possible, I'm hoping to find it so it doesn't destroy my cat and make me have to "fix" it with a reciprocating saw, a hammer, and a long metal rod.

If you've got any ideas where to look, that's what I'm looking for.

Nah I grew up in the car business and I drive older beat to hell cars for 5 hours daily. I know my smells. Good news is I think I know cause. I've been waiting for a new symptom and something popped up. Yesterday there was an occasional slight misfire. Today cylinder 5 has no fire coming out of the coil and cylinder 2 has about half strength. They run out of the same coil on that car. Since I just sent one of these cars to car heaven after stripping a few parts, I happen to have a complete ignition module. I'm betting weak sparks caused a carbon buildup over time. That buildup was breaking up occasionally and burning off. I'm likely to smell a smell coming from the exhaust pipe because I'm stopping and going in very short distances. I could be wrong though.

Bad news is that if I'm right I'll see a p0420 code soon.

You have to bear in mind that mail route cars see rather extreme usage conditions daily. For example, the front wheels get too hot to touch daily from the brakes being constantly used about 700x. Transmissions get overheated if you push the vehicle too hard. Cooling systems are a pain. When the radiator starts leaking, I know that I'm probably going to be doing a water pump and maybe a heater core soon too. Long running hours and repetitive use are hard on these cars. Constantly dipping on and off of the road wears out your suspension quickly. Wheel alignment isn't even worth trying to keep up with. I go down dirt roads aiming for the smallest pot holes.

I think you get where I'm going. This is why I use 20+ year old cars. They're cheap.

I pulled the wire from that coil and started it. Nothing. I then pulled it while the car was running. Shade tree mechanic trick, I know. As till nothing If the coil was good, it should've zapped me. Those coils will make sparks jump a few inches from the coil to a wire or a grounded spot if they're working. The zap will make you make up words. Not a thing. Swapped the coil with one of the old ones, runs like a champ again.