1. will a DP make your exhaust louder, yes it will and since you already have the hks cat back it will. by how much i don't know.

2. which DP is the best? well that is a matter of personal opinion. the hks is good though it is not a 3" but it will make power and should bolt up to your stock cat. for a full 3" Buschur, AMS, Megan, Helix, all come to mind, but since those are 3" don't think the bolting flange will fit the stock cat.

3. Will you pass cali smog? I don't know, i don't live in cali, but since you will be running the stock cat you should be ok, even a high flow cat you should be fine ( i think don't know how strict the smog test is with a high flow cat).

Hope that helps!

 

thanks man

 

The HKS is a pretty quiet cat back. Even with a 3" downpipe it's a pretty mellow exhaust.

 

oh ok thanks