I have the B&B pipes instead of Sharkwerks so same idea. However, I have the same leak that you do. I tightened the clamps until I could tighten no more, adjusted the clamps, etc. Nothing I could do would stop the leak. Mine is quite minor and can only barely be felt if you hold your hand up to it. I figure it isn't hurting anything unless someone smarter than me says otherwise.

 

I also have the B&B pipes along with the Gundo hack on my 997.2 C2 but can't honestly say that I hear any "leakage". If there is.... Great! Since it would only add to the below 3,500RPM sound that I think is still a bit tame. Above that... sweet!!

 

That's not how exhaust resonance works.

 

My sharkwerks bypass leaks a little. All the ones I've seen on other cars did too. My brothers Tubi exhaust did too in same place.

 

I used new clamps since mine were pretty rusty. And zero leak.
If you change them, go with the OEM as i used aftermarket ones and they leaked, changed to OEM and perfect seal.
Also use a torque wrench to not over tight then.

 

Thanks all. Tightened a little more and reduced leak. Drove it today for 300 miles. Checked and no issues