I have an '87 na s4, with the air pump, rats nest, and 6 port actuators removed. Over the weekend I removed the stock exhaust, and installed a RB header, with aftermarket presilencer and Dynomax mufflers. So no cat.

It smokes constantly now, I can't tell if it's white or blue smoke. The only thing that changed was the exhaust. Almost no smoke before the exhaust change.

Here is what I changed:
RB header (leak at the flange because I damaged one exhaust stud)
Full aftermarket exhaust
Removed the air line to the cat, which left an opening under the intake manifold.

I thought the air line to the cat wouldn't matter, since the air pump and 6 port actuators are gone. Am I right?

On the flip side, the power increase was impressive, much more than I expected. But now I have a mosquito fogger... any ideas?

 

When does it smoke? sounds like bad oil control rings. does it get better with the car warmer? the removal of the cat made the problem worse.

 

It seemed consistent from cold start to running warm. Why would removing the cat make it worse?

 

cuz CAT removes bad stuff, including some "smoke."

if I leave my S5 for a week or 2, it always smokes like **** for the first 5-10 minutes. then its fine. oil control rings are going.

 

Would running it for 10 minutes on the road so it fully warms up lessen the smoke? Like posted above it is common that bad oil rings cause smoke on startup after sitting a few days. How many miles on the engine? Either you have bad rings or you connected a vacuum hose incorrectly when doing your "delete".

 

I ran it for about 15 minutes; maybe that wasn't long enough, esp since I put a syringe of oil in the lower spark plug hole to get it started. No idea on miles on the motor.

The car is new to me, so I don't know much history. The "delete" was done before me, as was the hack electric fan ziptied to the radiator.

It's not street legal; I'll run it this Friday at a drift event, hopefully it will stop smoking after 10 minutes. Otherwise... hey, no mosquitoes!

Should I worry about the open port where the cat air line connected under the intake manifold?

 

The open port is fine, I would at least cover it with a rubber cap so moisture doesn't go in. You will need to run it a bit more if its residual oil burning off, if it's bad oil rings thats just the way it is.