the center-to-center measurement for the bolts on the flanges are the same.

the "hole" in the flange where the exhaust flows through is just bigger on the 3".

 

Thanks for the response man!

 

Got another question for you guys, once the hfc and DP are in place, will I have any problems when running these parts without my tune? I will be running stage 2 cobb map but for trips to dealer, etc I will be flashing back to stock, just making sure the car will run fine without a tune, etc.

 

the DP and cat will not affect anything that would require a tune.

the turbo will just spool better/quicker........

..........due to the initial increase in exhaust velocity

 

good deal. and you guys that are running it without a tune, any cels?

 

never had a CEL.

just be very careful when you remove the o2 sensor from the stock cat.

 

So I got the UR HFC put on today, love the extra power and sound. Odd thing is, after it was installed, I am now getting what sounds like a squeeky skateboard wheel type noise when I turn left??? Any ideas what that might be guys?