i am finishing up my exhaust and i have the following problem: my downpipe is 3", then it will have to connect to a 2.5" fake cat, then back to a 3" catback. Is this going to affect my tune negatively? I was tuned on an open downpipe. Thanks.

 

yes you placed a restriction in the exhaust... its no longer a 3"

 

Yes. Buy a 3" test pipe.

So many stupid questions on here lately. SMH

 

i guess my real question is, will i be ok to run it like this for a week or so, Are my afr's going to change that much?

 

You will be ok to run it like that. AFR's may richen up a bit. You will likely lose power, but you won't be hurting anything.

 

just stay out of boost until you fix it... thats a disaster in boost though especially right after the downpipe

 

Common sense answers most of these questions.