Not true. I had BERK HFC on my stock exhaust for acouple weeks before my exhaust arrived. I didnt have any rasp.

 

Thats actualy good to know.

 

I take that back. Thinking about it I did have a little. During normal driving there was done, the only time I heard any rasp was in first or second gear when I would let the RPMs drop past 2500. Like coasting to a stop or something I would hear a little.

But once I put my exhaust on, it compeletly went away.

Also my BERK HFCs are wrapped in header wrap and ceramic coated, so it may have made a difference.