Exhaust leak causing rich AFR's??
 

ok so i have a very weird problem with my exhaust. when i baught my 2003 evo 8 it had a different downpipe and had a cat delete. the downpipe has a nut welded on it right before the cat delete that is the same size and thread as an o2 sensor. so i put a AEM Wideband o2 sensor in that hole and when i took it for a drive it blew my stock exhaust apart when fully boosted (when the inernal wastegate opened up). it blew apart at the resonator in the center of the car. i tried to repair multiple times and still would blow apart.

so i baught a new cat back exhaust and removed the sensor from the hole and drove it and it drove ok, very rich like always, but no issues with exhaust comming apart.

i went ahead and put the sensor back in because i didnt want that huge leak and sure enough it blew the bottom out of the 3 new gaskets i just put in for the new exhaust.
so i removed the sensor and im just dealing with this leak. i did replace the gaskets to.

could this leak be causeing my car to run very rich?????
ive baught everything i could think of to try to fix the rich problem and got me nowhere.
New plugs, 10MM wires, coil packs, MAF sensor, altonator, battery, IAC valve - because my car will come very close to stalling after taking it out of gear anywhere from 3,000 RPM's up, then will come back up to a good idle(smelling like gas horribly), and a new fuel pressure solenoid.

if anybody could give me some pointers that would be great!

An exhaust leak (if anything) would make the AFR's look leaner (if its before the O2 sensor) as the exhaust is getting diluted with fresh air.

I don't really understand how you're blowing your exhaust apart...is there a blockage in the system somewhere?

As far as you running rich:

1) Has it always ran rich since you bought it?
2) Is there a tune on the car?
3) What is your fuel pressure at?

It has ran rich since i got it. I dont know what all the guy did to it before me.

I put a new exhaust on so there should be no blockage. I did remove the silencer from the muffler today and it runs a little better but still really rich when i boost. And when i come out of the throttle it just drops down to like 2-300 rpms and about stalls then comes back up to 1100. (Smelling like gas horribly)

On idle it misses every so often. Not bad but it just gets loaded up with fuel the wormer it gets. Its driving me insane lol.

Idk my fuel pressure.