I installed one of these this weekend. Purchased on eBay on a Monday and was at my house Friday (the day after Thanksgiving). I do have PSE and it sounds great. With the PSE off it's hard to tell a difference from stock.

 

I had the sharkwerks X pipe installed on my car... a 2011 GTS... a few months ago. I'm happy with the results. It's definitely louder across all RPMs, though the intensity varies IMHO.

It is slightly louder at idle, but considerably louder when the engine is under load at say 4 - 5K RPMs. There seems to be no drone at cruising speed. I think they have built a nice product.

Highly subjective, but I'd estimate the sound is perhaps 30% louder than OEM... noticeable, but not crazy.

 

Is there any truth that any crossover pipe, regardless of design, causes a noticeable vibration in the cabin at idle?

 

 

None with the Tubi on my -09 C4S and none with my current SW.

 

nope