well i took of my exhaust manifold in search of the source of my leak, and i found something odd.

What is that round hole in the center plate? My car is an 87 (s4), but i know the motor was swapped at one point. So im not sure if the motor is s4 or s5 or what. Either way, im pretty sure exhaust is coming out of that hole, as there is soot around that area. I was thinking it might be for egr, and i am considering plugging it with a freeze plug or something similar. Does anyone know what it is or what i can do about it?

 

s4 n/a engines had a core plug(freeze plug in other words) in that spot to block the exhaust flow out, you should be able to find a metric plug at your local auto parts store to replace the one that blew out.

 

ok, so do i also have to worry about why it blew out?

also, does anyone know if its a 21 or a 22?>

 

could be any of a few reasons, most likely i can think of is excessive backpressure in the exhaust aka a failed catalytic converter.

not sure on the exact size since i haven't seen one blow out before.

 

well i figured it out. 21.44 mm plug fit perfectly. i looked at the cat before i put it all together, and it looked pretty bad. ill have to take care of that soon. at least MN has no emissions tests!