my friend was rear-ended about a week ago,the insurence company sold his FC (s4 N/A)to a near by junk yard,so knowing that he had the engine rebuilt about a year ago and also had a R/B header,the ACV blocked off and the 5th and 6th ports wired up with chicken wire(idle reasons..i guess?) i decided to wait for the junk yard to pull the motor and i would go buy it-$300 why not. i got the motor and came to find out that they had cut the R/B header right after the collector. so my question is can i bolt the stock s4 N/A manifold back on while leaving the ACV blocked off and not run the air pump? the car its going into is an s4 with the stock pre-cats and cat with 3inch cat back.

 

Why not just take it to an exhaust shop and have them weld on a new piece to connect to the cat? And yes, it will work, but it'd be a bad idea.

 

I wouldn't use the stock cats without the ACV and split air pipe. You will torch that cat in no time and cause major problems.