So I finally got an exhaust on the car and it runs great. Ive been trying to find excuses to take the E30 for a drive. I couldnt say that just even a week ago. I was a horrible ride with just headers, but I think it still runs a little rich. The shop that did my exhaust combined the headers into a Y straight to a single Cat back to a resonator then exhaust tip. The whole sys restored ALOT of my low end torque. But one weird thing is that the Magnaflow Cat I ordered has an o2 port right in the middle of the cat. The welder made an extra just behind the cat, so all 4 o2's are in. Im almost certain this is why im rich. But my question is, will it hurt anything? Long term, short term. Iv heard a lot of people talk about cylinder wash. That almost sounds as bad as elbow grease and headlight fluid. The exhaust actually smells very sweet. But it still has a hint fuel. Chocolate came to mind the very first time I cranked her up with pipes all the way to the rear. Somtimes it will smell quite metallic and sweet at the same time. Today I could swear it was smelling like oranges. kind of tangy. At first I thought coolant but, when it was just headers, it just smelled like an old burning car when it ran. Help me out here but I cant see any correlation between putting pipes on a car and coolant leaking into the motor. 
Anyway, is running rich harmful in any way?
Anyway, is running rich harmful in any way?