Just got my Fast Intentions HFC's installed and now I can say I have a smile on my face finally. Every time I hit the gas now I know I have an exhaust under there. Still not very loud at WOT though but can't win them all ( for 2k though I should........). Two things that I wish FI intentions changed were the location of the bungs (02 sensor cable does not fit correctly in stock harness anymore or it would be too tight) and the brace underneath the cats can no longer be used. Other than that, pretty stoked.

 

It is a good feeling. I felt the same when I got my RHFC's installed. I had the same problem with the brace btw.

 

How bad is your hiss at decel? It's almost comically loud for me (even in the cabin) but that's only when I heard it just revving from neutral. I'll have a buddy drive my car around the block to see what it sounds like when it's moving.

 

What hiss? No hiss here.

 

Oh wow, is that the difference between Resonated and non because if so, damnit. LOL. Or maybe it's the fact you still have the stock exhaust where I have the FI catback.

Next time you are in your car Rochester roll down your windows and rev the car in neutral. If there is no hiss present when the rpms fall back down then you indeed have no hiss so lucky you. I'll take a video of mine to show you what I'm talking about.

 

I thought you bought the resonated cats. That could be the difference. I'd suspect that more than the cat-back. That, or a leak. After a while, go back to your mechanic and have him eyeball the fitment on everything, and check for leaks, after it's had a few weeks to settle in. That's a reasonable follow-up for an aftermarket exhaust.

As for that cross-member that bolted your OEM cats to the frame... I still have mine. Looking right at it, in fact. It's always been the plan to have my guy come up with some way to weld connectors to the new cats, and put that back on. I'm not comfortable having all that weight hanging off the headers.

 

Have you checked to make sure that everything is tightened down?

 

I have quite a bit of decel hiss on my system with HFC and FI catback. It was even louder when I swapped in an unresonated X-pipe. The 12" FI systems did allow a lot of the his to come through but was slightly muffled.

 

There is a video of LAnce in his 370 and he has the RHFC's and I hear the same sound so dunno.

Also, I had the same worry as you concerning not being able to reuse the cross member so maybe I need to go to an exhaust shop and see if they can fabricate something for me.

Everything was impacted so pretty sure it is.

Yup, what's your feeling on it?

 

Next time you get a chance Rochester, can you take pic of your cross member under your HFC's. If it's not attached how does it not vibrate?

 

Here's a crazy thought... someone slap me for silly if it's stupid.

What about buying rear coil-overs. Just rears.

 

Found the video I was talking about of an example of hiss on deceleration.

 

That noise on decel that sounds like a turbine winding down?

No it's not attached. Here it is on my dining room table.

There was quite a bit of at-idle vibration after the install. So I removed the heavy rubber damper nubs that were attached to the mid-pipes, and the vibration all but went away (mostly). You don't have that option, because you don't have the OEM cat-back anymore, so IDK what to say, except maybe to put this cross-member back on, like we're talking about.

Have to come up with some creative way to weld bolts with bushings to match up with the original holes on the ends. Hmm. Anyway, here it is:

 

Ok, I'll bite.....why?

 

I have a heavy decel hiss as well, FI RHFCs and 12 inch resonated exhaust. John when you go CBE it will likely become a bit more pronounced.