Huge, huge, huge difference, actually.

Indeed^^^ That's the soul purpose of the actual resonators, and they do their job quite nicely!

This is incorrect as well. You're comparing a 300 Cell Cat...to a fully free flowing Test Pipe. The ART pipes are definitely louder then the FI HFCs combos.

Hi, I got the 18" SS FI,
I find the drone at high way cruising speed just tolerable.

I shouldn't even consider the RHFC/ berk HFC right? either of those would increase drone?

Thanks,
Alan

I have FI RHFCs with 18" RCBE. Adding the cats does increase it.

:icon18: My ear might already got the HUGE damage from the non-res FI exhaust! LOL

But you forgot ART pipes are not regular test pipes. That's what that 2 "grenades" for. They are resonators. And as you just stated yourself they do their job quite nicely.;) Here is the sound level from what I heard people were talking for years.

Test pipes > HFCs > ART pipes > RHFCs

Be honest tho, HFCs and ART pipes are very similar. Test pipes are louder for sure. But then again, like I posted earlier, my ears might already got damaged! LOL