About a week ago, my olds started running poorly. Weak struggled accel, bad vibrations at high speeds, and what seems to be exhaust under the hood.
The car is running very rich, and therefore is sort of stinky. This is making it hard to try and smell what it is. If i had to guess, I would assume the rear manifold (or close to it) may be leaking.
Is there a common reason to experience this?
I will be re gasketing/replacing my intake parts in the very near future, and I have spare manifold parts and gaskets, but I don't want to start pulling exhaust parts off the car if I don't really need to.
My issue is when I pull all the intake apart, it will be easy to get to, but I will be unable to turn it on to see where this smoke may be coming from.
The smoke seems to be coming from the rear of the engine, but it is really hard to even tell. I could be way off track on the source.
If anyone has any clever ideas, or better yet, has experienced this themselves, I would love to hear from you.

P.*
We changed the plugs and wires when it ran funny last week (no help)
We checked all coil packs (they all tested at 6.5ish i believe)
I swapped out the EGR for a new EGR I had handy (no change)
I checked for vacuum leaks (didn't find any)
I removed and cleaned the MAF, and I think my plenum is beginning to seep a little, so I am looking for one currently.
The MAF was filthy, but it seems ok (when unplugged the car suffers and stalls)
This all happened very suddenly. I was driving the night before and it was perfect. Went to work the next day, and it began struggling hard after about 5 mins on the highway.

Thanks again